Test that we can get a subdirectory from a tarball (or any other
"packed" source that we support).
The 'tar-subdir-to-parent' test highlights a regression where the
subdirectory module references a module in its parent directory. This
breaks the intended use ofr the subdirectory and the implementation in
go-getter. We need to fix this in terraform, and possible plan warnings
and deprecations for this type of source.
James Bardin