Refactor, use new work queue helper

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

src/service.h

@@ -36,6 +36,7 @@ void      service_reload_dynamic (void);
 
 int       service_step           (svc_t *svc);
 void      service_step_all       (int types);
+void      service_worker         (void *unused);
 
 void      service_bootstrap_cb   (uev_t *w, void *arg, int events);