Fixes #50. Use clTimerDeleteAsync during healthcheck timer delete. This would avoid deadlocks when a running healthcheck timer callback tries to grab the cpmMutex also taken by the synchronous clTimerDelete that would wait for any running healthcheck timer callbacks to finish. And it can't because of the deadlock on the mutex. Using clTimerDeleteAsync would ensure that the deletion would be safe even under the mutex shared with the timer callback
Fixes #51. Use SA_NOCLDWAIT and SIG_IGN to handle zombies for amf children instead of using a sigchld handler to reap children/zombies with a waitpid on all children