AOD: Fix navbar flicker when transitioning to AOD

Under certain circumstances, the transition to AOD can happen before
the navigation bar gets a chance to hide itself, which happens in a
traversal. To work around this, post turning the screen on such that
it only happens after the next traversal.

Change-Id: I178b9394e7cc6baa8e9552c9819c3ce9b044defb
Fixes: 64599221
Test: Open Whatsapp / Gmail, turn off screen, verify navbar does not flicker.