Fix AnimatedImageVisual not rendering well if ReleasePolicy is not DETACHED

Fix AnimatedImageVisual not rendering well if ReleasePolicy is not DETACHED

Their are some logical issue if we use ReleasePolicy as DESTROYED or NEVER
and SceneOff+SceneOn again cases.

Current ImageCache system not consider non-empty queue case when we call
FirstFrame();

Rather to fix the logic, let we simply clear the cache before re-call
FirstFrame();

Since we remove texture cache at processor time, Clear cache immediately
will not make any side effects.

Change-Id: Idbc1a2cc62724ff67b84554cc94dc7168fa7f942
Signed-off-by: Eunki Hong <eunkiki.hong@samsung.com>