Hide AoD wallpaper after 1min

Hide wallpaper by cross fading back scrim. This increases
battery life since black pixels won't drain power.

Bug: 64155983
Test: atest packages/SystemUI/tests/src/com/android/systemui/statusbar/phone/ScrimControllerTest.java
Test: set AoD wallpaper, wait for 1 min.
Test: set AoD wallpaper, wait for 50 sec, go to pulsing, wait 10 sec.
Change-Id: Ie830c2fd20f9e60efbfd9e78f248603df07ae93c