MFC r335899:

auditd(8): register signal handlers interrutibly

auditd_wait_for_events() relies on read(2) being interrupted by signals,
but it registers signal handlers with signal(3), which sets SA_RESTART.
That breaks asynchronous signal handling. It means that signals don't
actually get handled until after an audit(8) trigger is received.
Symptoms include:

• Sending SIGTERM to auditd doesn't kill it right away; you must send SIGTERM and then send a trigger with auditon(2).
• Same with SIGHUP
• Zombie child processes don't get reaped until auditd receives a trigger sent by auditon. This includes children created by expiring audit trails at auditd startup.

Fix by using sigaction(2) instead of signal(3).

Cherry pick https://github.com/openbsm/openbsm/commit/d060887

PR: 229381
Reviewed by: cem
Obtained from: OpenBSM
Differential Revision: https://github.com/openbsm/openbsm/pull/36