Fedora libvirtd fails to start on Xen instances (i.e. rackspace
instances) due to [1]. This works around the issue until it can be
fixed upstream.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1098376
Change-Id: I3790b5025982730263a6a84fce596e80f09efd5a