Check if the stream can be disabled by the zen mode

This change reworks onStart `{ volumeDialogController.getState() }`
invocation because in this case the new state is emitted before the
`VolumeDialogCallbacksInteractor` is ready to process the upcoming values.

Flag: com.android.systemui.volume_redesign
Fixes: 388510417
Fixes: 388508798
Fixes: 388455787
Fixes: 388454510
Test: atest VolumeDialogSliderInteractorTest
Test: atest initialEvent_isSubscribedToEvents
Change-Id: Id92a54a75f0f95fa01ea9df32bf1e16c0df17393