Remove usages of isDisplayOccluded

The single occluded state should be only used inside KeyguardController.
The outer accesses should use isKeyguardOccluded that considers whether
keyguard is active.

Also removed ATMS#isKeyguardLocked which was no longer used.

Fix: 297188512
Test: atest ActivityRecordTests#testCompleteFinishing_showWhenLocked
Change-Id: I474015a36802e46f2448686f2f175e8e84e14956