Comment 7 for bug 1599636

There is currently no mention of this workaround at [1] and since it is too easy to miss this when doing upgrades I think we should bump priority (and fix the guide).

[1] https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-upgrade-openstack.html#cinder-ceph-topology-change-upgrading-from-newton-to-ocata