Fix the copr owner/user disagreement.

This will make us ready to catch the change in messages coming with this
upstream patch:
https://lists.fedorahosted.org/pipermail/copr-devel/2014-August/001085.html
Fix copr usernames() method.
Merge pull request #140 from fedora-infra/feature/copr-owner-fix

Fix the copr owner/user disagreement.