'Return tuple (exists, name).'

def _rbd_image_exists(self, name, volume_id, client, try_diff_format=False):

    rbds = self.rbd.RBD().list(client.ioctx)
    if (name not in rbds):
        LOG.debug("Image    '%s'    not    found    -    trying    diff    format    name", name)
        if try_diff_format:
            name = self._get_backup_base_name(volume_id, diff_format=True)
            if (name not in rbds):
                LOG.debug("Diff    format    image    '%s'    not    found", name)
                return (False, name)
        else:
            return (False, name)
    return (True, name)
