mds: fnctl. add get_waiting_overlaps function; fix get_overlapped locks so that it won't do bad things if there aren't any.
mds: fnctl. add get_waiting_overlaps function; fix get_overlapped locks
so that it won't do bad things if there aren't any.

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