Comment 30 for bug 1665698

@Christian: what does the default /etc/qemu-ifup do?

Although I'm inclined to accept your argument that my recent change to Nova was a step in the wrong direction, I'm wondering why it seems to work (at least in my testing) in practice.

Also, if there was now a change in libvirt to interpret '' as "do nothing", is there something straightforward we could put in the Nova code to detect when libvirt has that fix - and so set '' - and when it doesn't - in which case best to set None.