Allow performShowLocked when transition animation started

Some transitions can have no animation, in which case
isReadyForDisplayIgnoringKeyguard() will wait for VIEW visibility
to become VISIBLE. But if we have a saved surface, the transition
could have already started. This causes exiting app to be hidden,
while entering app's performShowLocked() still hold back waiting
for the relayout to visible.

If we started animating with saved surface, it should also count
as transition animation started.

b/30855380

Change-Id: I6260a323b48e57d8337267d9136f630226a48dc8