Use the pidfiles while checking status of worker/verifier

In cases where workers and verifier are running on the same system, as $DAEMON is /usr/bin/python, service stacktach status will say running if verifier is running and workers are stopped, and vice versa.  In fact, service stacktach/verifier status will say 'running' if *any* python process is running when the check is made.  Using the pidfile gets us more accuracy here.