core/service: call service_enter_running() if live mount fails

service_enter_running() would re-arm timer for RuntimeMaxSec=,
hence it should be called instead of disabling timer completely
when live mount operation fails, in a similar fashion as
service_enter_reload_by_notify().

src/core/service.c

@@ -5299,7 +5299,7 @@ static int service_live_mount(Unit *u,
 
 fail:
         s->live_mount_result = SERVICE_FAILURE_RESOURCES;
-        s->timer_event_source = sd_event_source_disable_unref(s->timer_event_source);
+        service_enter_running(s, SERVICE_SUCCESS);
         return r;
 }