ovb jobs on vexxhost fail with "Unable to establish connection to https://rdo.vexxhost.ca:5000/v3/auth/tokens"

OVB jobs on Vexxhost such as periodic-tripleo-ci-centos-8-ovb-1ctlr_1comp-featureset002-train fail in

  TASK [ovb-manage : Create a stack]

with error message [1]:

  keystoneauth1.exceptions.connection.ConnectFailure: Unable to establish connection to https://rdo.vexxhost.ca:5000/v3/auth/tokens: HTTPSConnectionPool(host='rdo.vexxhost.ca', port=5000): Max retries exceeded with url: /v3/auth/tokens (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7f7f07804630>: Failed to establish a new connection: [Errno 111] Connection refused',))

According to mnaser on irc.oftc.net #vexxhost, the old endpoint

  https://rdo.vexxhost.ca:5000/v3

has been deprecated a while ago and has been replaced with

  https://identity.rdo.mtl2.vexxhost.net

He restored the old endpoint to give us some time to fix our config repo.

[1] https://logserver.rdoproject.org/openstack-periodic-integration-stable4/opendev.org/openstack/tripleo-ci/master/periodic-tripleo-ci-centos-8-ovb-1ctlr_1comp-featureset002-train/3c1b505/job-output.txt