Add a failsafe check to prevent display surfaces from remaining hidden

Since there appear to still be some races in the keyguard + dream
logic, add a failsafe to prevent display-areas from getting stuck in
hidden state. This should be pretty rare.

Bug: 300790517
Bug: 289861878
Test: existing tests pass. This is a failsafe for a rare race.
Change-Id: I6f89d8b9a9e1aa1b8673fcaffe4c1b92c4c3d210