Core: Correct HLE Event Callbacks and other issues.

src/core/hle/kernel/synchronization.cpp

@@ -28,6 +28,7 @@ void Synchronization::SignalObject(SynchronizationObject& obj) const {
                 time_manager.CancelTimeEvent(thread.get());
             }
         }
+        obj.ClearWaitingThreads();
     }
 }