Initiate KeyguardDisplayState with default display state

This change is to initiate the new KeyguardDisplayState with the default
display state for newly added display. Otherwise, the default value will
be used and the KeyguardController and other related classes will treat
the newly added display as unlocked even if the default display is
locked.

Bug: 436770343
Test: Add new display when locked, nothing other than the clock should
      be shown
Flag: EXEMPT BUGFIX
Change-Id: I005837226dbc4e1e20b9233bd0fd5ed18dfcd1af