We want to be able to use "dns=none" (without peer-to-peer gossip)
even for clusters that have the k8s.local extension. These were
previously called "gossip clusters", but really that is an
implementation; what actually matters to users is that they don't rely
on writing records into a DNS zone (such as Route53).
We add the hosts plugin to CoreDNS, and we populate a ConfigMap from
kops-controller (when in gossip mode).
This enables resolution of the internal apiserver DNS name from Pods,
even when gossip mode (k8s.local) is in use. This should fix the
failing e2e tests which are assuming that the name in the JWT token is
resolvable from inside the cluster.
This is also a possible step towards a simpler gossip mode, now that
we have a central controller.
justinsb