Update KeyguardViewMediator field to primitive type.

Currently we are seeing exceptions due to the fact that the
mShowCommunalByDefault field is an un-initialized boxed Boolean type
instead of a primitive boolean with a default of false.

Bug: 333699753
Test: WIP - adding in follow-up item
Flag: NA
Change-Id: I08e1d7bbfede036dbc6a3189a5e6d5fa6cbe8080