bash-config and tcsh-config don't uninstall cleanly

[jdreed]

Because /etc/profile.d/profile.debathena.sh is a config file, it does not get removed without a purge, however we do remove our run-parts directories. So profile.debathena.sh then tries to run-parts in an empty directory, and prints annoying things to stderr for SSH connections.

We should test -d those before executing run-parts. And possibly fix #594 at the same time.