Test nova server (VM) boot in overcloud job

We use the demo script from kolla ansible, init-runonce, to create
resources in the control plane to make it ready for booting a VM. We
then create a nova server, and wait for it to become active. We do not
currently test that the VM boots successfully by accessing it via SSH.

Change-Id: I61be554366565decd9f4ff7805a3969aa37da4b9