Comment 1 for bug 870405

I suggest we replace the current 'nova-manage_flagfile_location.patch' with this one.

We should also try to get this upstream.
The change here is basically to try to use /etc/nova/nova.conf only if it exists and is readable.
While that still will break you if you're running nova-manage from a source tree as root on a system with nova installed, i find that scenario unlikely.