I.e. don't exit with the signal number, instead set the signal handler
to the default one and then raise it again.

Noticed while trying to dump the stack at segfaults in the 'perf test'
forked process used to run each test, that inspects signal info at
each test.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-5x5r176wnoqxi5p6id05wv9w@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>