mds: fix and use add_replica_stray() helper for handle_dentry_unlink
mds: fix and use add_replica_stray() helper for handle_dentry_unlink

Eliminate duplicate code by using (and fixing) the helper.

Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

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