It doesn't appear that Red Hat has created a new RPM for RDO on Fedora 21 yet:
https://repos.fedorapeople.org/repos/openstack/openstack-icehouse/fedora-20/
You could manually update the file /usr/lib/python2.7/site-packages/cinder/image/glance.py - line 434, to look like:
output[attr] = getattr(image, attr, None)
to see if this resolves your issue.
