Fade away wallpapers when long pulse

Add back timeout wallpaper while docking pulses due to docking pulses
may took a long time and should fade away wallpaper to avoid aging.

Reset mWallpaperVisibilityTimedOut flag to reset wallpaper timeout every
time scrim state changed or panel expanded.

Fix: 135134059
Test: atest SystemUITests:ScrimControllerTest
Change-Id: I5ea3e52733734cef6c6850fa4af1d8ad2941f967