Send display-OFF event if that is initial state.

Local Displays have always sent an initial state of something
other than OFF.  With foldables, thats not the case any more so
don't ignore state_off events if the device's state was previously
UNKNOWN.

Bug: 178713651
Test: manual, atest com.android.server.display
Change-Id: Icc426c289e59aad43dc5d6fb0033fbbc887b0270