FileStore.cc: Fix error in collection_rename
FileStore.cc: Fix error in collection_rename

Previously, the rename operated on the collection names.  Now, rename
operations on the full paths to the collections.

Signed-off-by: Samuel Just <9c2b0c5e50ef18bfc3944e6192d76b07115a3b95@gmail.com>

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