load and unload scene before loading and unloading is done

[Wanfanel]

in ScenePartLoader load and unload scene before loading and unloading is done can duplicate scenes
to avoid this we needed check if scene is fully load/unload with something like this:

        IEnumerator IsDone()
        {
            isloadCompleted = false;
            while (!asyncOperation.isDone) { yield return null; }
            isloadCompleted = true;
        }