Check for header when restoring default clock.

This change tracks the state of the header in the smart space while a
custom clock is showing so that the correct digital clock size can be
restored when switching back to the default clock face.

Fixes: 135534500
Test: visual - take phone of dock and check size of default clock
Change-Id: Id4d1d46c94d8480f9675a3cf682a20a9706ba707