Print DNS commands when launching a node.

Still not automatic, but much less typing.

Change-Id: I348b866db3f2778ba08a516a00d258358c4a9129
Reviewed-on: https://review.openstack.org/22468
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins