- Factoring: reduced the (repeated) generation of the remote cached name into make_cached_name()
- Fixed bug: Table that records what files are cached should use the name under which they are cached.
Remove unnecessary make_cached_name/free pair.
Merge pull request #222 from dthain/work-queue-cache-cleanup

Factor the (repeated) generation of the remote cached name into make_cached_name(). And fix master to keep track of the contents of the worker's cache directory using exactly the names under which the file is stored there.