Lls: Use LlsController for checking LLS focus

We're trying to keep track of this state in too many places.  The
LiveLockScreenController keeps track of the LLS focus so this patch
adds a method to get the state of the LLS focus and use that instead
of cached values that may not be in sync.

Change-Id: I2cbf1122b8a27cb1b0ee1ed93379a362308db5bd
TICKET: CYNGNOS-2849