Add Ubuntu slaves to CI

Closing this for now as the VM is up and running.

I created ubuntu1404-vm01.phx.ovirt.org so that we can check what's needed on ubuntu. It's just a minimal install. Please check if you need anything specific on this box or we can close this. At least I think we need to adjust these manifests to support non-RPM distros if we need more VMs:

https://gerrit.ovirt.org/gitweb?p=infra-puppet.git;a=blob;f=site/ovirt_jenkins_slave/manifests/base.pp

Another issue I hit on the way was this bug:
http://projects.theforeman.org/issues/7384

Changed the provisioning template to hardcode hostnames during build, now Foreman provisioning works reliably. Also created a "ubuntu_hosts" host groups with just the users as most of our other manifests are RPM-only and will not work.

Tried to use the image from Glance but some of oVirt's issues don't let us use it normally:
1) when a VM is created from glance-imported template, the boot flag is removed thus making it useless
2) there's no option to extend the disk by means of oVirt
Even after creating a VM, extending the disk, setting boot flags and saving a new template I got to the next issue:
3) oVirt only applies cloud-init settings in "Run Once" mode which is not the mode used by foreman

So effectively there is no point in using this cloud image for VM provisioning. We'd need to manually edit its metadata and then remove cloud-init as it's useless.
I deployed a VM via foreman directly instead, same as we do for reference Fedora images. Will report once it's ready as there's some issues with puppet.

The latest LTS version is 14.04 so as discussed this is the version our slaves will run. added this version to Glance so I'll use it as a base for our slaves.