Change method of tracking moving AppWindowTokens.

Stop trying to keep track of the AppTokens that have been moved
to the top and bottom and then try and match the WindowStates when
transitions are goodToGo. Instead rebuild the WindowState order based
on the AppToken order when we are goodToGo.

When moving AppWindowTokens lower in mAppTokens create a new ArrayList
of AppWindowTokens to keep track of the apps in Z order while
animating.

Fixes bug 6481078.

Change-Id: I29b33a507b45752f15feb10a9f4b47a3f5eb9f0e