Fix issues #5233826 and #5209847 -- live wallpapers.

5233826	when a live wallpaper starts, it does so regardless of its visibility

The WallpaperService is now very forceful about telling a wallpaper it is
not visible when it first starts.

5209847	Make launcher turn off the wallpaper in all apps.

Fix a bug in the window manager that would not correctly handle the wallpaper
flag changing.

Change-Id: Ie3314043a84664be72a1304a1705408efd789a15