Changes

ttcn3-asterisk-ims-ue-test: show trace on coredump

Use wrapper_core_bt_on_error.sh to show a backtrace in case asterisk
crashes and a coredump is generated. Set CWD to /data, so the core and
core.backtrace files end up in the jenkins artifacts.

The result looks like this (forced a segfault in main() to test this):
  $ cat asterisk-ipv4/core.backtrace
  [New LWP 18]
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  Core was generated by `/usr/sbin/asterisk -C /etc/asterisk/asterisk.conf -f -g -vvvvv -ddddd'.
  Program terminated with signal SIGSEGV, Segmentation fault.
  #0  0x000073908c476ffb in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  #0  0x000073908c476ffb in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  #1  0x00005ba2677294dc in memset (__dest=0x0, __ch=1, __len=1) at /usr/include/x86_64-linux-gnu/bits/string_fortified.h:59
  #2  main (argc=<optimized out>, argv=0x7fff865fdd28) at asterisk.c:3839

Change-Id: Iee22cbeaa2b2c136c789afc3ebd3ec1be10a6ac7