Restore KeyguardBottomAreaView state

KeyguardBottomAreaView will be re-inflated when the theme changes,
it's necessary to also restore some of its internal state, otherwise
we'll have NPEs.

Test: manual
Test: atest KeyguardBottomAreaTest
Fixes: 117121386
Change-Id: Idac8192877b65f8ad00cd60a2bb0c1ce75476cf1