mds: don't adjust subtree map in rename_prepare
mds: don't adjust subtree map in rename_prepare

Not sure what the reasoning behind this was.

This code is from pre git history, and the git->subversion conversion
managed to make pretty git-blame unusable.  I doubt I really documented
what its purpose at that point was anyway.

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