Enable internal cluster DNS by deploying CoreDNS in the kube-system
namespace. It covers dns queries for both the cluster and external,
acting as a proxy with a cache layer in front.
Version of CoreDNS hard-coded to 007, image taken from dockerhub.
Related-Bug: #1692449
Change-Id: I0a9703b531fe872416dcd79fa7d4d27c1ea61586