LLS: Fix screen off event firing when not interactive

Track PowerManager's interactivity to accurately report screen off.
While we did not get the screen on when in ambient display, the
screen off event would still fire.  Keep track of the interactivity
and send screen off event accordingly.

Change-Id: I633cacbf3a5d22b416e1bd6550d7b8d661c16c3d
TICKET: CYNGNOS-2519