Make rhsm_repos major version specific and delete obsoleted repos.
This should delete all the repos that have been obsoleted by rhel entitlements. @kdreyer please double-check that I've removed the right ones or if there are others that we should remove.
Also, trying to activate rhel 7 repos on a rhel 6 node fails. I've made rhsm_repos major version specific and added the rhel 6 repos we want to enable to fix that.