Don't cache shouldAttachNavBarToAppDuringTransition

Navigation bar can be removed at the runtime. This CL invokes
DisplayPolicy#shouldAttachNavBarToAppDuringTransition when needed
instead of caches it in the constructor of RecentsAnimationController.

Fix: 276274274
Test: atest RecentsAnimationControllerTest ZOrderingTests
Change-Id: I4d70855c946802185ac6502a9f2d00afb60f14f2