Fix shell interpolation in Ruby strings...

Apparently I have been writing too many shell scripts recently, because the
dollar sign is not how you trigger interpolation in a Ruby script.

This fixes that to use Ruby interpolation, resulting in a string that works
the way it was expected.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Merge pull request #399 from daniel-pittman/feature/master/388-handle-updated-internal-package-repo-layout

Fix shell interpolation in Ruby strings...