Fix screenshot not showing up on subsequent screenshots

The static screenshot view wasn't getting set back to alpha=1 on
reset, so it was effectively invisible. This change resets it and
returns to animating out the background protection.

Bug: 219790596
Fix: 219790596
Test: manual; observed taking screenshots in quick succession (while
the screenshot was animating out) to see that the alpha wasn't reset,
and was after the change

Change-Id: I3afc4e97fd1cd28a1cf9988be0c519590dca7b30