Migrate system+lock wallpaper to lock-only when setting live wp

If the static imagery is shared between system+lock, preserve the lock
presentation when setting a different system-surface live wallpaper.  If
the caller knows it wants to achieve system+lock display of the new live
wallpaper, it follows up setWallpaperComponent() with an explicit clear
of the lock wallpaper state.

Previously, setting a new system live wallpaper would necessarily override
a desired static lock image in the case of system+lock shared imagery.
Now it doesn't.

Bug 32664317

Change-Id: I7ef2cded534f9e6e91899db4c37bd24efaf09fee