Use kvm for the cd-overcloud.
Use kvm for the cd-overcloud.

It defaults to qemu in devtest_overcloud, and we definitely don't want
qemu in prod.

Change-Id: Ic14a556daa26efabdf0a101e3cc2047f74be56ec

rdo-management/tripleo-image-elements,openstack/tripleo-image-elements,radez/tripleo-image-elements,openstack/tripleo-image-elements,rdo-management/tripleo-image-elements,radez/tripleo-image-elements