Fix for #122

This is a fix for #122
Always use original location instead of shadow-copied location when loading RProvider plugins.
@jack-pappas wrote the original fix, but didn't fix the RInteropClient, so I took his pull request and redid in for RInteropClient as well.

If I know how to add to jack's pull-req as myself, I would do that, instead I simply pulled his req and amended it.