Fix issue with alphas not being applied to the same view on unlock

- It's possible for the nav bar configuration to change between locking
  and unlocking the phone, which will prevent the alpha from being
  restored on the bar layout correctly. This change updates the alpha
  of both vertical/horizontal layouts in NavBarView since they should
  always be in sync.

Bug: 206733387
Test: atest SystemUITests
Test: Lock screen in landscape app, turn screen on and unlock


Change-Id: I265d04e6e2192f2bb57b1f8d77390664236427fc