On occlusion: use AUTH_SCRIMMED scrim state

Previously, it was using AUTH_SCRIMMED_SHADE because
when an app is occluding the lockscreen, the status
bar state is StatusBarState.SHADE. Therefore, we need
to make sure that if we're occluding (and the shade is
not expanded), that the AUTH_SCRIMMED scrim is used.

On devices where clipQs=false, using AUTH_SCRIMMED_SHADE
instead of AUTH_SCRIMMED would make the alternate bouncer
have a black background instead of showing a transparent
scrim over the occluding activity.

Fixes: 272101893
Test: atest CentralSurfacesImplTest
Test: show the alternate bouncer over an occluding app,
 scrim is transparent over occluding app
Test: show the alternate bouncer over the shade on top
 of an occluding app => frontScrim is transparent over
 the notification shade. Back & notification scrims are
 the same as what they'd be for the regular open shade

Change-Id: Ie3b2d3ff7868eb038023787e5cae35c98576f5fe