launch_daemon: Trigger sticky-already-triggered external events immediately.

If the external event is sticky and already triggered, then we want
to trigger any newly-added events immediately. This fixes "boot hangs
on rocket" regressions following 4f126f690c,
which seems to have exacerbated this already-existing race condition.

Fixes #17289.

Change-Id: Ie405826cc50255895c8831c34b8bdf902e584eb5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4510
Reviewed-by: waddlesplash <[email protected]>

src/servers/launch/LaunchDaemon.cpp

@@ -317,6 +317,9 @@ ExternalEventSource::ResetSticky()
 status_t
 ExternalEventSource::AddDestination(Event* event)
 {
+	if (fStickyTriggered)
+		Events::TriggerExternalEvent(event);
+
 	if (fDestinations.AddItem(event))
 		return B_OK;