Automatic merge from submit-queue (batch tested with PRs 38294, 37009, 36778, 38130, 37835)
Add a cloudprovider validator flag to kubeadm and update the DNS spec
Broken out from: https://github.com/kubernetes/kubernetes/pull/37568
This PR creates a flag for `cloud-provider` that validates the value before `RunInit()` is run, which makes it now act as a "real" flag
Then it removes the `k8s.io/kubernetes/pkg/cloudprovider` dependency, which makes the binary ~40MB smaller! That's _really_ worth it!
In the second commit, the DNS addon is updated to the latest version: https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns/skydns-rc.yaml.base
@kubernetes/sig-cluster-lifecycle
aa08702d23