MClientRequest: handle owner_uid and owner_gid from ceph_mds_request_head_legacy
When a client is too old and uses struct ceph_mds_request_head_legacy we must
fill new owner_uid and owner_gid fields from an old client_uid and client_gid.
Fixes: https://github.com/ceph/ceph/pull/52575 Fixes: https://tracker.ceph.com/issues/63288 Fixes: commit 46cb244b9c839 ("ceph_fs.h: add separate owner_{u,g}id fields") Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>