When a TERM signal is received, the listener parent process will wait
for all child processes to complete any active tasks before killing the
child processes and shutting down.
Receiving a SIGINT or SIGQUIT results in a non-graceful shutdown.
In all cases, the system first un-registers with all routers.
Signed-off-by: Bill Erickson <berick@esilibrary.com> Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>