Fix issue where window would be marked as opaque

When launching an app, we need to keep the window marked as transparent
until the animation is over, otherwise the app window won't be visible.

Test: manual
Test: atest NotificationShadeDepthControllerTest
Test: atest ActivityLaunchAnimatorTest
Fixes: 191874111
Change-Id: Id075b802c72d99ed457ab6e2f9dd97e1bc46a01a