perf evlist: Reset SIGTERM handler in workload child process

Jiri reported hanging perf tests on latest acme's perf/core and bisected
it to 87f303a9f:

[jolsa@krava2 perf]$ cat /proc/sys/kernel/perf_event_paranoid
1
[jolsa@krava2 perf]$ ./perf record -C 0 kill
Error:
You may not have permission to collect %sstats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid:
 -1 - Not paranoid at all
  0 - Disallow raw tracepoint access for unpriv
  1 - Disallow cpu events for unpriv
  2 - Disallow kernel profiling for unpriv

Need to let default handling kickin for workload process.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1369525839-1261-1-git-send-email-dsahern@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>