nrf52_bsim: Fix: shell return code should be != 0 on ASSERT

When calling posix_print_error_and_exit()
a return != 0 was not provided to the shell
This was due to thee way the tracing functions call back
into the main app exit function, assuming that callback
will return.
But in the SOC_INF boards, that function does
not return, and the tracing functions never have the
chance to exit(!=0)
Fix it by calling posix_exit() in the wrap function instead.

Signed-off-by: Alberto Escolar Piedras <alpi@oticon.com>