Make the parent worker process automatically restart
hung or dead child processes.
The parent will check all the child processes every 30 sec
to make sure they are still running. If not they will be restarted.
Also child processes update a heartbeat timestamp periodically
while processing messages. If the parent detects that that timestamp
hasn't been updated in a configurable amount of time (default 600sec)
it terminates the old process and spins up a new one.
Change-Id: I28ffbe64391d04a6e85b7e197393352ee1e978b0
82aca32286