More targeted version of "Correct animation glitch for pinned stack."

See the referenced CL "Correct animation glitch" for an explanation of
why an exception in this area is required. That CL based the exception
off the dummy animation state, however it seems we also enter this
state in various docked transitions but in that case the dummy animation
will have the incorrect transforms referenced by the original comment.
Now we target the fix on the bounds animating state instead.

Bug: 37448295
Bug: 36777039
Bug: 37511473
Test: Dock app from recents, no stretching. Auto-pip app, doesn't get stuck in top-left. Yay!
Change-Id: I5c9a7384622de9cedcc4be4dec7caacf58c683eb