Fixing issues with alpha 0.0 on parent view.

Parent view should remain with 1.0 alpha.
Container view should fade when switching starts, and come back
to alpha of 1.0 once the switching has been completed.

Fixes: 78309123
Fixes: 78309400
Test: Visual confirmation of various flows. Switching to user with a pin. Canceling bouncer. Switching to user without a pin. Turning the screen off and back on after unlocking the user first.
Change-Id: I17946a1feea20bcb2fd2603c8cba0f2f51acd65d