SystemUI: add hook to block monet from applying its overlays

if we want to use our own custom overlays this prevents
the final set enable of the monet overlays.

this does not block creating the fabricated overlays on
wallpaper change so when monet is enabled again they
are already there and will be used

Change-Id: I17ca85f6f5108bd70f4e79ef142a129f249d0a20
2 files changed