Kubeadm should support running master as unschedulable

[andrewrynhard]

When running kubelet with --register-schedulable=false, kubeadm hangs because it creates addons.

[luxas]

This will probably be possible when we've refactored the kubeadm API: #100

[pires]

I believe that at least the network add-ons should run on master too but would advise for DNS as well (the mandatory add-ons).

[luxas]

This is done via a master taint. Kubelet should not be run with --register-schedulable. Instead kubeadm automatically taints the master which makes it reject all pods except for kube-discovery, kube-proxy and kube-dns

[luxas]

I think this issue can be closed