Comment 2 for bug 1263251

Looks like this bug is caused by this change:
https://review.openstack.org/#/c/63175/4/nailgun/nailgun/db/sqlalchemy/models/release.py

I think what happens is that when RedHat release is added to the NailgunDB, the ceph-osd role gets deleted from the CentOS release that was added previously. Ubuntu is added after RedHat, that's how its ceph-osd role remains intact.