Fixes notifier restart error when last notifier is deleted

This actually isn't a large issue, since the HAL automatically creates a
notifier at the beginning to handle the time rollover, but during
testing without that, I noticed that deleting the last notifier would
disable notifiers for the entire lifetime of the program. This seemed to
be caused by the CLOSEST_TRIGGER static variable not being reset, and
causing new notifiers to never be added to the queue. This fixes that.
Not a bug that can be seen normally, but still a bug.

Change-Id: I6ac61c632918c90972cd0664aa833e3bc9e8c535

hal/lib/Athena/Notifier.cpp

@@ -125,6 +125,7 @@ void cleanNotifier(void* notifier_pointer, int32_t *status)
 			delete notifierManager;
 			notifierManager = nullptr;
 		}
+		closestTrigger = UINT64_MAX;
 	}
 }