mds: non-head requests always rdlock as_anon
mds: non-head requests always rdlock as_anon

This ensures we can't do a snapped GETATTR and rdlock with EXCL on a
directory and miss out on cap metadata still with the client.

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph