Prevent NSSL flicker on SHADE->AOD

Prevent a flicker when the shade is expanded and the user
hits the power button. This will perform an eased fade out.

Fixes: 326228196
Test: atest SharedNotificationContainerViewModelTest
Flag: ACONFIG com.android.systemui.migrate_clocks_to_blueprint
STAGING

Change-Id: Ifd8afb3de2a21e779e1b0bbbeafb26c7007c3128