'Update the subnet with new info.
The change however will not be realized until the client renew the
dns lease or we support gratuitous DHCP offers'

@db_api.retry_if_session_inactive()
def update_subnet(self, context, id, subnet):

    (result, orig) = self._update_subnet_precommit(context, id, subnet)
    return self._update_subnet_postcommit(context, orig, result)
