MClientRequest: handle owner_uid and owner_gid from ceph_mds_request_head_legacy

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>
(cherry picked from commit a70a70f589214d6e2a5b477a61005b13ba2fec46)