Wait for transitions in cuj10p/e

This is a follow up of I7e7dc3b2f05bd8bf9b87fb7c5d6f997a0a6be4cb.
Disconnecting an external display also triggers a transition.

Flag: EXEMPT - test stabilization
Bug: 442453305
Bug: 442453123
Test: atest WMShellSmokeTestsDesktopMode
Change-Id: I7305d131c414b12e4cfd6b81ab895badc5b14435