dlt-user: fix address sanitzer issue

[alexmohr]

This PR fixes an issue found by asan.
As I side effect I cant reproduce #522 anymore.

In general it might be a good idea to add a pipeline step where the unit tests are run with -fsanitize=address and maybe other sanitizers gcc (or clang) offers

exiting
    #0 0x7ffff7625fc6 in __interceptor_sigaltstack ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:9986
    #1 0x7ffff768c493 in __asan::PlatformUnpoisonStacks() ../../../../src/libsanitizer/asan/asan_posix.cpp:44
    #2 0x7ffff769202c in __asan_handle_no_return ../../../../src/libsanitizer/asan/asan_rtl.cpp:612
    #4 0x7ffff7073ac2 in start_thread nptl/pthread_create.c:442
    #5 0x7ffff710584f  (/lib/x86_64-linux-gnu/libc.so.6+0x12684f)

 at offset 160 in frame

  This frame has 2 object(s):
    [32, 88) 'log_new' (line 5017)
    [128, 160) 'handle' (line 5016) <== Memory access at offset 160 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
Thread T37879 created by T0 here:
    #0 0x7ffff762a685 in __interceptor_pthread_create ../../../../src/libsanitizer/asan/asan_interceptors.cpp:216

SUMMARY: AddressSanitizer: stack-buffer-overflow ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:9986 in __interceptor_sigaltstack
Shadow bytes around the buggy address:
  0x10007e637b10: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 f8 f2
  0x10007e637b20: f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 00 06
  0x10007e637b30: f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007e637b40: 04 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00
  0x10007e637b50: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00
=>0x10007e637b60: 00 00 00 f2 f2 f2 f2 f2 00 00 00 00[f3]f3 f3 f3
  0x10007e637b70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007e637b80: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
  0x10007e637b90: f1 f1 00 00 f2 f2 f8 f2 f2 f2 f8 f8 f2 f2 00 00
  0x10007e637ba0: 00 00 00 00 00 00 00 00 00 00 00 f3 f3 f3 f3 f3
  0x10007e637bb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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
  Shadow gap:              cc
==3067906==ABORTING
Process finished with exit code 1

The program was tested solely for our own use cases, which might differ from yours.
Licensed under Mozilla Public License Version 2.0

^{Alexander Mohr, alexander.m.mohr@mercedes-benz.com, Mercedes-Benz Tech Innovation GmbH, imprint}