Secondary question: Is there a way I can lock out the offending versions of yum-rhn-plugin from my local mirror until RH fixes the problem ? I am trying removing the RPMs from the repo_mirror, put "exclude=yum-rhn-plugin" in /etc/yum.conf and trying a "cobbler reposync"
I will report back my results.
No, unfortunately I don't think reposync supports blacklists of any kind, and cobbler is just a wrapper around the standard CLI tools.