We think we have growing pains in some clouds where ipv6 is available
but we want to force the instances to use ipv4 dns anyway. We can do
this by telling nodepool to use ipv4 for the instance ip which we can
then check in our role to configure unbound.
Do this to rule out ipv6 as a problem in these clouds.
Change-Id: I354015df64032e70422231f1105807f024fe2393
7d5673f6db