Ignore AnimationFinishedCallback when we call Animation::Clear() hard + Resolve bug...

Ignore AnimationFinishedCallback when we call Animation::Clear() hard + Resolve bug when we call Play multiple times

There was several bugs at AnimationPlayList.

1. Core::ProcessCoreEvents sequence is like this :
     SceneEvent -> NotificationManager -> Relayout -> Flush.
   If we call Animation::Clear() at SceneEvent timing, Notfication will send animation finished signal
   what we must not send.

   To avoid this system, let we store the cleared animations at AnimationPlayList.

   Since AnimationFinished callback required at least 1 frame times after flush,
   we can ignore whole notify events before Flush done.

2. Scene mPlayList keep the reference of Animation whenever we call Play, there
   were several problems. For example, If we call Play() 2 times and Clear(),
   that Dali::Animation never be removed.

Change-Id: Ie9d5298311b9e5318fecad21b1124c896fcf3a8e
Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>