Git cookbook caching was not working.

Currently, a git location cookbook cannot be retrieved from cache and will always be cloned on every install. This is simply because the cache? method is looking for a revision_path based off of name-branch. When a cookbook is stored, it is always stored with name-ref. So the cached cookbook can never be retrieved. I'm not sure what the original desired behavior was, but all I did was make the storage and retrieval align. The specs were updated to reflect this.

Thanks