Comment 5 for bug 1765271

Try to use use `cert_manager_type = x509keypair`, then restart magnum-api.service and magnum-conductor.service, reference https://wiki.isu.kim/isus-wiki/openstack/magnum-troubleshooting#1.-failed-to-create-certificates-for-cluster.

or fix the bug of barbicanclient of magnum that update magnum/common/clients.py and magnum/tests/unit/common/test_clients.py, reference https://storyboard.openstack.org/#!/story/2010629 and https://review.opendev.org/c/openstack/magnum/+/880820.