Revert "services: don't clear wallpaper when SystemUI"

This reverts commit fb2840a98928be2fd02ec5ac98a16c8a21506c0c.

Change-Id: Ib23bd688f690c51afe2115cc7497d3cf508a091e
Merge "Revert "services: don't clear wallpaper when SystemUI"" into kitkat-caf