Revert "Bug 836293 - Lockscreen wallpaper is not updated after changing homescreen wallpaper r=timdream"

This reverts commit 27bfddddd1d99f91b17dd9c7aaad9f9c496dca7c.
Revert "Merge pull request #7686 from Rik/banding-jones-829075"

This reverts commit dfc2b0d9bc828270da10eccfd30ace0c88730fad.