Make DN specification optional
Since condor 7.9.0, clients no longer need to specify DNs of condor daemons for secure GSI auth. The same host checks are performed as with Globus GRAM. Of course, some sites may have host certs which do not match the hostname -- for this case, we should definitely keep the DN allowed.
I would like to request making listing the DNs optional if the frontend / factory can confirm it is running at least 7.9.0. If the condor version is not known, we should fall back to requiring them to be safe.