perf tests: Initialize sa.sa_flags

The sa_flags field is not being initialized, so a garbage value is being
passed to sigaction.  Initialize it to zero.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1456923322-29697-1-git-send-email-colin.king@canonical.com


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