Fix #280: allow calling initctl restart foo from within foo

Move the stop+start from initctl to the state machine by allowing
stopped tasks to restart once it has been collected.  This should
prevent finit from blocking, allowing it to handle other requests
while waiting for the service's PID to be collected.

Effectively, this will allow a service to call initctl to restart
itself, as reported in issue #280.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/service.h

@@ -40,6 +40,7 @@ int       service_timeout_cancel (svc_t *svc);
 
 void      service_forked         (svc_t *svc);
 
+int       service_stop           (svc_t *svc);
 int       service_step           (svc_t *svc);
 void      service_step_all       (int types);
 void      service_worker         (void *unused);