BUG : dvc cache partially used when packages are pulled

[AlexVCaron]

There is a bug in the DVCFilesystem when a package in a DVC repository is fetched. The packages gets placed in cache and at its desired location, fine. This makes it so if the package is pulled once again, it is not downloaded from the web. However, the way the package is created at the desired location doesn't honour the DVC configuration passed. We want to create links from the cache to the desired location, but right now it's copied. iterative/dvc-data#513 will solve this problem