It looks like setting ceph_nova_keyring before the upgrade fixes the problem. On the cluster where I had already run the upgrade, I set ceph_nova_keyring in globals.yml to ceph.client.nova.keyring and then redeployed, and that fixed it.
It looks like setting ceph_nova_keyring before the upgrade fixes the problem. On the cluster where I had already run the upgrade, I set ceph_nova_keyring in globals.yml to ceph.client. nova.keyring and then redeployed, and that fixed it.