Revert "CM11 Themes: Clear wallpaper mixnmatch entry on external change"

This reverts commit c04aa2c0e5a10af7e5d099e9aaaf57923a06e92f.

Change-Id: Iad15eb2b3b3c38ba707196ebc36b29e28631967f
Merge "Revert "CM11 Themes: Clear wallpaper mixnmatch entry on external change"" into kitkat