Core/GameObject: Skip setting state of NewFlag, if new state is equivalent to old state

Port From (https://github.com/TrinityCore/TrinityCore/commit/6175467c3e66fa09d8ff1e0f091375c26f7529e5)

Source/Game/Entities/GameObject/GameObject.cs

@@ -4401,6 +4401,9 @@ namespace Game.Entities
 
             public void SetState(FlagState newState, Player player)
             {
+                if (_state == newState)
+                    return;
+
                 FlagState oldState = _state;
                 _state = newState;