Ensure dozeTimeTick refreshes clock

... by sending a time update via the KeyguardUpdateMonitor path.
Smartspace also listens to this signal.

Also, cleanup flag for backgrounding the alarm

Fixes: 393470511
Test: manual - observe prolonged AOD state
Flag: EXEMPT bugfix
Change-Id: Ic2d7658f2bbb40521f2e95fb2157affd6f753979