Unocclude immediately so that the surface animation is visible.

Prior to ag/17776445, a bug caused WM to call setOccluded(false)
for us at the start of the animation. Fixing that bug revealed
this one - the animation on the occluding surface does not
render if we think we're occluded.

Bug: 230436724
Test: occlude/unocclude
Change-Id: I5a6bbabdc74fbd671c0a84d811cb6c22651f1fb1