'Get an available backup service host.
Get an available backup service host in the specified
availability zone.'

def _get_any_available_backup_service(self, availability_zone):

    services = [srv for srv in self._list_backup_services()]
    random.shuffle(services)
    idx = 0
    while (idx < len(services)):
        srv = services[idx]
        if (self._az_matched(srv, availability_zone) and srv.is_up):
            return srv.host
        idx = (idx + 1)
    return None
