openshift.ks: Clean up repo config comments

Delete comments for configure_*_repo functions, most of which state the
obvious, and a couple of which are wrong.

Add comments to configure_repos when defining need_*_repo to explain _why_
we configure particular repos.
Merge pull request #72 from Miciah/openshift.ks-clean-up-comments-on-repo-config

openshift.ks: Clean up repo config comments