Fix Glanceable Hub timeout with scene container

Also make sure the scene container doesn't change scene if the device is
locked while on dream or communal scene.

Additionally, SceneInteractor#changeScene and
SceneInteractor#snapToScene should be called on the main thread, so make
sure of that in the CommunalSceneInteractor.

Test: atest CommunalSceneStartableTest
Test: atest CommunalSceneInteractorTest
Fix: 365598818
Flag: com.android.systemui.scene_container
Change-Id: I3e476192d0563fc408a02b85c3306897b5c9591f