Directories.migrateFile() does not handle -old or -tmp LDB manifests

During LDB compaction a -old.json file is created with the previous manifest.

Directories.migrateFile() only checks for the .json extension and uses the length to determine the CF name.

This can result in the -old.json manifest getting copied to a CF-old directory in the new layout.

see http://www.mail-archive.com/user@cassandra.apache.org/msg27583.html for an example