bluestore/bluestore_types: check 'it' valid before using

When sanitizer is enabled, unittest_bluestore_types fails as following
```
[ RUN      ] sb_info_space_efficient_map_t.basic
=================================================================
==143714==ERROR: AddressSanitizer: heap-buffer-overflow on address 0xffff99f8b7f4 at pc 0xaaaab50bde18 bp 0xffffebefcdb0 sp 0xffffebefcda8
READ of size 8 at 0xffff99f8b7f4 thread T0
    #0 0xaaaab50bde14 in sb_info_t::get_sbid() const /root/ceph/src/os/bluestore/bluestore_types.h:1337:30
    #1 0xaaaab50a5908 in sb_info_space_efficient_map_t::find(unsigned long) /root/ceph/src/os/bluestore/bluestore_types.h:1385:10
    #2 0xaaaab50bd638 in sb_info_space_efficient_map_t::_add(long) /root/ceph/src/os/bluestore/bluestore_types.h:1424:15
    #3 0xaaaab50a52bc in sb_info_space_efficient_map_t::add_maybe_stray(unsigned long) /root/ceph/src/os/bluestore/bluestore_types.h:1358:12
    #4 0xaaaab4fec03c in sb_info_space_efficient_map_t_basic_Test::TestBody() /root/ceph/src/test/objectstore/test_bluestore_types.cc:113:11
    #5 0xaaaab51e9a40 in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2605:10
    #6 0xaaaab5197040 in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2641:14
    ceph#7 0xaaaab51488a4 in testing::Test::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:2680:5
    ceph#8 0xaaaab514a7e8 in testing::TestInfo::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:2858:11
    ceph#9 0xaaaab514bde8 in testing::TestSuite::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:3012:28
    ceph#10 0xaaaab5167bac in testing::internal::UnitTestImpl::RunAllTests() /root/ceph/src/googletest/googletest/src/gtest.cc:5723:44
    ceph#11 0xaaaab51f3940 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2605:10
    ceph#12 0xaaaab519e5d8 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2641:14
    ceph#13 0xaaaab5167024 in testing::UnitTest::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:5306:10
    ceph#14 0xaaaab50b4d6c in RUN_ALL_TESTS() /root/ceph/src/googletest/googletest/include/gtest/gtest.h:2486:46
    ceph#15 0xaaaab50a1080 in main /root/ceph/src/test/objectstore/test_bluestore_types.cc:2847:10
    ceph#16 0xffff9d6c73f8 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    ceph#17 0xffff9d6c74c8 in __libc_start_main csu/../csu/libc-start.c:392:3
    ceph#18 0xaaaab4f3812c in _start (/root/ceph/build/bin/unittest_bluestore_types+0xe4812c) (BuildId: cb75399658026f83a4e89012de8fb02f08f6d239)

0xffff99f8b7f4 is located 0 bytes to the right of 20-byte region [0xffff99f8b7e0,0xffff99f8b7f4)
allocated by thread T0 here:
    #0 0xaaaab4fe636c in operator new[](unsigned long) (/root/ceph/build/bin/unittest_bluestore_types+0xef636c) (BuildId: cb75399658026f83a4e89012de8fb02f08f6d239)
    #1 0xaaaab50c0d2c in mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t>::allocate(unsigned long, void*) /root/ceph/src/include/mempool.h:375:33
    #2 0xaaaab50c0c0c in std::allocator_traits<mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t> >::allocate(mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t>&, unsigned long) /usr/bin/../lib/gcc/aarch64-linux-gnu/11/../../../../include/c++/11/bits/alloc_traits.h:318:20
    #3 0xaaaab50c044c in std::_Vector_base<sb_info_t, mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t> >::_M_allocate(unsigned long) /usr/bin/../lib/gcc/aarch64-linux-gnu/11/../../../../include/c++/11/bits/stl_vector.h:346:20
    #4 0xaaaab50bf954 in void std::vector<sb_info_t, mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t> >::_M_realloc_insert<long&>(__gnu_cxx::__normal_iterator<sb_info_t*, std::vector<sb_info_t, mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t> > >, long&) /usr/bin/../lib/gcc/aarch64-linux-gnu/11/../../../../include/c++/11/bits/vector.tcc:440:33
    #5 0xaaaab50be0d8 in sb_info_t& std::vector<sb_info_t, mempool::pool_allocator<(mempool::pool_index_t)11, sb_info_t> >::emplace_back<long&>(long&) /usr/bin/../lib/gcc/aarch64-linux-gnu/11/../../../../include/c++/11/bits/vector.tcc:121:4
    #6 0xaaaab50bd760 in sb_info_space_efficient_map_t::_add(long) /root/ceph/src/os/bluestore/bluestore_types.h:1429:24
    ceph#7 0xaaaab50a5e78 in sb_info_space_efficient_map_t::add_or_adopt(unsigned long) /root/ceph/src/os/bluestore/bluestore_types.h:1361:15
    ceph#8 0xaaaab4feb07c in sb_info_space_efficient_map_t_basic_Test::TestBody() /root/ceph/src/test/objectstore/test_bluestore_types.cc:103:11
    ceph#9 0xaaaab51e9a40 in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2605:10
    ceph#10 0xaaaab5197040 in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2641:14
    ceph#11 0xaaaab51488a4 in testing::Test::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:2680:5
    ceph#12 0xaaaab514a7e8 in testing::TestInfo::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:2858:11
    ceph#13 0xaaaab514bde8 in testing::TestSuite::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:3012:28
    ceph#14 0xaaaab5167bac in testing::internal::UnitTestImpl::RunAllTests() /root/ceph/src/googletest/googletest/src/gtest.cc:5723:44
    ceph#15 0xaaaab51f3940 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2605:10
    ceph#16 0xaaaab519e5d8 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /root/ceph/src/googletest/googletest/src/gtest.cc:2641:14
    ceph#17 0xaaaab5167024 in testing::UnitTest::Run() /root/ceph/src/googletest/googletest/src/gtest.cc:5306:10
    ceph#18 0xaaaab50b4d6c in RUN_ALL_TESTS() /root/ceph/src/googletest/googletest/include/gtest/gtest.h:2486:46
    ceph#19 0xaaaab50a1080 in main /root/ceph/src/test/objectstore/test_bluestore_types.cc:2847:10
    ceph#20 0xffff9d6c73f8 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    ceph#21 0xffff9d6c74c8 in __libc_start_main csu/../csu/libc-start.c:392:3
    ceph#22 0xaaaab4f3812c in _start (/root/ceph/build/bin/unittest_bluestore_types+0xe4812c) (BuildId: cb75399658026f83a4e89012de8fb02f08f6d239)

SUMMARY: AddressSanitizer: heap-buffer-overflow /root/ceph/src/os/bluestore/bluestore_types.h:1337:30 in sb_info_t::get_sbid() const
Shadow bytes around the buggy address:
  0x200ff33f16a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f16b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f16c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f16d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f16e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x200ff33f16f0: fa fa fa fa fa fa fa fa fa fa fa fa 00 00[04]fa
  0x200ff33f1700: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f1710: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f1720: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f1730: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x200ff33f1740: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==143714==ABORTING
```

'it' might be invalid, so before using 'it', need to figure validity out

Signed-off-by: Rongqi Sun <sunrongqi@huawei.com>
(cherry picked from commit e1c9294)

src/os/bluestore/bluestore_types.h

@@ -1315,7 +1315,7 @@ struct sb_info_space_efficient_map_t {
 	  [](const sb_info_t& a, const uint64_t& b) {
 	    return a < b;
 	  });
-	if (it->get_sbid() == id) {
+        if (it != aux_items.end() && it->get_sbid() == id) {
 	  return it;
 	}
       }