Postpone destroying leash until after cancel callback.

Currently we may end up releasing the leash (via Transaction#remove)
before setting mCancelled on the animation. This means if another frame
executes we could attempt to use a released surface. Here we cancel before
releasing the surface, careful not to disturb other logic.

Bug: 124112773
Test: Fixes them allegedly
Change-Id: I920a1c8f891a5cdc53b1d55298f661abc91b3259