SystemUI: show visualizer in shade-locked view

This brings back the behavior we had in 12.1 - visualizer would still be
visible in the shade locked state.

Also with the following improvements:
    * use less alpha
    * always attach/detach in a background thread (Async task)
    * use the statusbar state instead keyguard view state listener

Change-Id: I6b8a57f9f0bba6ba0591de0cb1f94a0eb904cc1c
Signed-off-by: Roman Birg <roman@cyngn.com>