Fix restart logic of sysv start/stop scripts and forking services

Init script return pretty quickly after launch, so we cannot use that to
detect if they, or the daemon they launched, have crashed.  So we start
the service_retry() with a 2 sec delay, which should be ample time to
allow the pidfile plugin to detect a forking service's new PID.

In release-cycle regression, no public issue needed.

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

src/service.h

@@ -38,6 +38,8 @@ void      service_update_rdeps   (void);
 int       service_timeout_after  (svc_t *svc, int timeout, void (*cb)(svc_t *svc));
 int       service_timeout_cancel (svc_t *svc);
 
+void      service_forked         (svc_t *svc);
+
 int       service_step           (svc_t *svc);
 void      service_step_all       (int types);
 void      service_worker         (void *unused);