Fix auth_url type
Fix auth_url type

In this case, auth_url variable is set as Tuple.
It is bug, so this fixes it.

Change-Id: I524749df95cc0cf67fd30d637632e8430dc04e17

openstack/magnum,Tennyson53/SUR,annegentle/magnum,ddepaoli3/magnum,ChengTiesheng/magnum,ffantast/magnum,ffantast/magnum,annegentle/magnum,sajuptpm/magnum,ddepaoli3/magnum,eshijia/magnum,jay-lau/magnum,LaynePeng/magnum,hongbin/magnum,openstack/magnum,Tennyson53/magnum,Tennyson53/SUR,Tennyson53/magnum,mjbrewer/testindex,ArchiFleKs/magnum,paulczar/magnum,LaynePeng/magnum,Alzon/SUR,mjbrewer/testindex,eshijia/SUR,paulczar/magnum,ArchiFleKs/magnum,dimtruck/magnum,eshijia/SUR,eshijia/magnum,hongbin/magnum,mjbrewer/testindex,ChengTiesheng/magnum,sajuptpm/magnum,Alzon/SUR,ramielrowe/magnum,dimtruck/magnum,ramielrowe/magnum