Return torrent path in content_files

For an unknown reason, currently only the filename is returned within content_files. This causes a plugin which wishes to download a file from a torrent containing directories to fail if the file desired is inside a directory.

Given this torrent structure:
MyTorrent
- MySampleDirectory
- - MySampleMovie.mkv
Currently content_files would only return MySampleMovie.mkv. Any plugin which uses that would fail to find the actual file on the server. deluge_path is insufficient as it only returns the path to the directory containing MyTorrent.