Lock Screen - Add Lockscreen Wallpaper (2/2)
PS3 add Default Wallpaper as option

PS4 fix preference list doesnt show selected item

PS7:
Rebased and modified to check for existence of a lock screen
wallpaper when updating the preference.

Change-Id: I2f4db0ddc132482d191eea4f76160b51b4063a60
Make sure custom lock wallpaper is readable by all.
Change-Id: Iaef5d7cd6c0426b0577127fd8bae1abd731aba4e