Run keyguard occlusion update after transitions

Earlier code was calling applyKeyguardOcclusionChange as soon as the
transition starts, which is not very effective because some of the
transitions only update keyguard occluded state at the end of the
animation and race behind this call.

If we wait for all transitions to finish playing before validating
keyguard occlusion, the last word always comes from
applyKeyguardOcclusionChange which synchronises the source of truth
in KeyguardController over to SystemUI.

Test: atest android.server.wm.KeyguardTests
Bug: 275650364
Change-Id: I016b72b87baadb63f3f5f83112901315f29d2f0a