Add example openstack config

The comments are what we might put in the Jenkins ~/.vagrant.d/Vagrantfile if we used this, but I'm inclined to leave them here for now as a "how-to" sort of thing.

Note setting the floating_ip manually is annoying as hell - it shouldn;t be necessary on something like OS1-internal which gives out routeable IPs by default, but otherwise you need it for Vagrant to reach the box.