Support7Demos: Reflect a status change of playback state properly

When item status is changed and the sample app is notified of it via
RemotePlaybackClient.StatusCallback#onItemStatusChanged, republish the
new playback state so that the controller dialog can be in sync.

Bug: 24958135
Change-Id: Ia6e2c3276798107d95376746cb06e6cad3b66fb8
1 file changed