Do not clear AppWindowToken.allDrawn while animating.

Creating new surfaces for applications clears the allDrawn flag in the
AppWindowToken. If the app windows were animating when this happened
the animation would complete immediately resulting in jank. This fix
defers clearing allDrawn until the animation completes.

Bug 7326635 fixed.

Change-Id: I5abe3b9ecfbefb476de6a6c8acc394373cc11751