Prevent a deadlock on process termination when using a SocketAppender

[swebb2066]

Remove termination debug message that is not output as the LogLog singleton has been detroyed.

[swebb2066]

For the record, using multithreadtest with XMLSocketAppender and no server listening on the TCP port, the deadlock is:

`(gdb) thread apply all bt

Thread 5 (Thread 0x7f45027fc640 (LWP 7473) "multithreadtest"):
#0 __futex_abstimed_wait_common64 (private=128, cancel=true, abstime=0x0, op=265, expected=7467, futex_word=0x7f4509a1b910) at ./nptl/futex-internal.c:57
#1 __futex_abstimed_wait_common (cancel=true, private=128, abstime=0x0, clockid=0, expected=7467, futex_word=0x7f4509a1b910) at ./nptl/futex-internal.c:87
#2 __GI___futex_abstimed_wait_cancelable64 (futex_word=futex_word@entry=0x7f4509a1b910, expected=7467, clockid=clockid@entry=0, abstime=abstime@entry=0x0, private=private@entry=128) at ./nptl/futex-internal.c:139
#3 0x00007f450a1b7624 in __pthread_clockjoin_ex (threadid=139934491063872, thread_return=0x0, clockid=0, abstime=0x0, block=) at ./nptl/pthread_join_common.c:105
#4 0x00007f450a4452c7 in std::thread::join() () from /lib/x86_64-linux-gnu/libstdc++.so.6
#5 0x00007f450a7c8259 in log4cxx::net::SocketAppenderSkeleton::close() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#6 0x00007f450a6efa91 in log4cxx::helpers::AppenderAttachableImpl::removeAllAppenders() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#7 0x00007f450a739ca4 in log4cxx::Hierarchy::~Hierarchy() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#8 0x00007f450a73eada in std::_Sp_counted_ptr<log4cxx::Hierarchy*, (__gnu_cxx::_Lock_policy)2>::_M_dispose() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#9 0x00007f450a714765 in log4cxx::spi::DefaultRepositorySelector::~DefaultRepositorySelector() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#10 0x00007f450a6f488a in log4cxx::helpers::APRInitializer::~APRInitializer() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#11 0x00007f450a166495 in __run_exit_handlers (status=0, listp=0x7f450a33a838 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at ./stdlib/exit.c:113
#12 0x00007f450a166610 in __GI_exit (status=) at ./stdlib/exit.c:143
#13 0x00007f450a1baee8 in __pthread_once_slow (once_control=0x557d5586a070 <multithread_logger(int)::exiting>, init_routine=0x7f450a443d50 <__once_proxy>) at ./nptl/pthread_once.c:116
#14 0x0000557d5585ea0b in multithread_logger(int) ()
#15 0x00007f450a445253 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#16 0x00007f450a1b5ac3 in start_thread (arg=) at ./nptl/pthread_create.c:442
#17 0x00007f450a247a40 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

Thread 4 (Thread 0x7f45037fe640 (LWP 7471) "multithreadtest"):
#0 futex_wait (private=0, expected=1, futex_word=0x557d5586a070 <multithread_logger(int)::exiting>) at ../sysdeps/nptl/futex-internal.h:146
#1 futex_wait_simple (private=0, expected=1, futex_word=0x557d5586a070 <multithread_logger(int)::exiting>) at ../sysdeps/nptl/futex-internal.h:177
#2 __pthread_once_slow (once_control=0x557d5586a070 <multithread_logger(int)::exiting>, init_routine=0x7f450a443d50 <__once_proxy>) at ./nptl/pthread_once.c:105
#3 0x0000557d5585ea0b in multithread_logger(int) ()
#4 0x00007f450a445253 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#5 0x00007f450a1b5ac3 in start_thread (arg=) at ./nptl/pthread_create.c:442
#6 0x00007f450a247a40 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

Thread 3 (Thread 0x7f450921a640 (LWP 7468) "multithreadtest"):
#0 futex_wait (private=0, expected=1, futex_word=0x557d5586a070 <multithread_logger(int)::exiting>) at ../sysdeps/nptl/futex-internal.h:146
#1 futex_wait_simple (private=0, expected=1, futex_word=0x557d5586a070 <multithread_logger(int)::exiting>) at ../sysdeps/nptl/futex-internal.h:177
#2 __pthread_once_slow (once_control=0x557d5586a070 <multithread_logger(int)::exiting>, init_routine=0x7f450a443d50 <__once_proxy>) at ./nptl/pthread_once.c:105
#3 0x0000557d5585ea0b in multithread_logger(int) ()
#4 0x00007f450a445253 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#5 0x00007f450a1b5ac3 in start_thread (arg=) at ./nptl/pthread_create.c:442
#6 0x00007f450a247a40 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

Thread 2 (Thread 0x7f4509a1b640 (LWP 7467) "multithreadtest"):
#0 futex_wait (private=0, expected=2, futex_word=0x557d5629c948) at ../sysdeps/nptl/futex-internal.h:146
#1 __GI___lll_lock_wait (futex=futex@entry=0x557d5629c948, private=0) at ./nptl/lowlevellock.c:49
#2 0x00007f450a1b9002 in lll_mutex_lock_optimized (mutex=0x557d5629c948) at ./nptl/pthread_mutex_lock.c:48
#3 ___pthread_mutex_lock (mutex=0x557d5629c948) at ./nptl/pthread_mutex_lock.c:93
#4 0x00007f450a762c30 in log4cxx::helpers::LogLog::debug(std::__cxx11::basic_string<char, std::char_traits, std::allocator > const&) () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#5 0x00007f450a7ca62e in log4cxx::net::SocketAppenderSkeleton::monitor() () from /home/stephen/build/logging-log4cxx/src/main/cpp/liblog4cxx.so.15
#6 0x00007f450a445253 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#7 0x00007f450a1b5ac3 in start_thread (arg=) at ./nptl/pthread_create.c:442
#8 0x00007f450a247a40 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

Thread 1 (Thread 0x7f4509f91b80 (LWP 7466) "multithreadtest"):
#0 __futex_abstimed_wait_common64 (private=128, cancel=true, abstime=0x0, op=265, expected=7468, futex_word=0x7f450921a910) at ./nptl/futex-internal.c:57
#1 __futex_abstimed_wait_common (cancel=true, private=128, abstime=0x0, clockid=0, expected=7468, futex_word=0x7f450921a910) at ./nptl/futex-internal.c:87
#2 __GI___futex_abstimed_wait_cancelable64 (futex_word=futex_word@entry=0x7f450921a910, expected=7468, clockid=clockid@entry=0, abstime=abstime@entry=0x0, private=private@entry=128) at ./nptl/futex-internal.c:139
#3 0x00007f450a1b7624 in __pthread_clockjoin_ex (threadid=139934482671168, thread_return=0x0, clockid=0, abstime=0x0, block=) at ./nptl/pthread_join_common.c:105
#4 0x00007f450a4452c7 in std::thread::join() () from /lib/x86_64-linux-gnu/libstdc++.so.6
#5 0x0000557d5585e237 in MultithreadTest::testMultithreadedLoggers() ()
--Type for more, q to quit, c to continue without paging--c
#6 0x0000557d5585dd42 in void LogUnit::runTest(abts_case*, void (MultithreadTest::)()) ()
#7 0x0000557d55860630 in abts_run_test(abts_suite, char const*, void ()(abts_case, void*), void*) ()
#8 0x0000557d55861c31 in abts_run_suites(abts_suite*) ()
#9 0x0000557d5585cbd0 in main ()
(gdb)
`