pve8to9: recognize the cephx key migration health checks

The old text asked the operator to resolve the health issues, which is
wrong advice here. A cluster on Ceph 19.2.6 or newer reports its
unmigrated cephx keys as insecure, and on a Bookworm kernel the client
keys cannot be migrated at all. Name the checks instead.

The noout flag is ignored together with them. pve8to9 itself
recommends setting noout before an upgrade, and a set noout raises a
Ceph health check of its own. Checks that are not part of the
migration still warn.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>