Check if keyguard is showing instead of occluded for compat UI.

This fixes an issue where compat UI is hidden even when keyguard is dismissed (but still considered occluded because the activity could occlude the keyguard).

Bug: 206627721
Test: atest SystemUITests:WMShellTest
Test: atest WMShellUnitTests:CompatUIControllerTest
Change-Id: I95f5b4d75d46a4958763c5ea3cdadb09b88f9836