Handle reception of a new MediaStatus.

def new_media_status(self, media_status):
        """Handle reception of a new MediaStatus."""
        casts = self._casts
        group_members = self._mz.members
        for member_uuid in group_members:
            if member_uuid not in casts:
                continue
            for listener in list(casts[member_uuid]['listeners']):
                listener.multizone_new_media_status(
                    self._group_uuid, media_status)