Don't update visual stability when lockscreen hasn't changed

We'd otherwise be updating on every frame of animations into or out of
the lockscreen!

Bug: 332558345
Fixes: 354065727
Fixes: 354081031
Fixes: 354763436
Flag: com.android.systemui.scene_container
Test: atest VisualStabilityCoordinatorTest
Change-Id: Ia1d3060867ba32757d20788d3b4fdc536fb737c5