Protect against surfaceController and hasSurface getting out of sync.

WindowStateAnimator.mSurfaceController is set to null whenever a
surface is destroyed and WindowState.mHasSurface is set to false
shortly after that. However, it is possible for them to get out
of sync in a couple of places due to exceptions or duplicate destroy.
Consolidated the call to set WindowState.mHasSurface inside a finally
block in WindowStateAnimator.destroySurface
Also, cleaned up the code a little to that it is more obvious what is
going on.

Bug: 27235356
Change-Id: I7e6d0c1fb015531c393ac86dcaebebd134fad612