Set the undercloud host name to 'undercloud'.
Set the undercloud host name to 'undercloud'.

This makes more sense than calling it 'ubuntu'.

Note: This will require an associated incubator change which
I will push momentarily.

Change-Id: I166b45a6ceb34635ed5ef7e29dd028f8c6a4cbe3

rdo-management/tripleo-heat-templates,trozet/tripleo-heat-templates,redhat-openstack/tripleo-heat-templates,openstack/tripleo-heat-templates,bcrochet/tripleo-heat-templates,dprince/tripleo-heat-templates,trozet/opnfv-tht,rdo-management/tripleo-heat-templates,trozet/tripleo-heat-templates,trozet/opnfv-tht,bcrochet/tripleo-heat-templates,wyg3958/tripleo-heat-templates,wyg3958/tripleo-heat-templates,trozet/opnfv-tht,dprince/tripleo-heat-templates,bcrochet/tripleo-heat-templates,openstack/tripleo-heat-templates,redhat-openstack/tripleo-heat-templates