Enable flagging a kubelet as a master node for tainting.

[svrc]

What this PR does / why we need it:
This enables labeling and tainting on master nodes that wish to deploy a Kubelet. This is the foundation to enable pluggable CNI support in CFCR.

How can this PR be verified?
Deploy CFCR with a kubelet on the master node. The node should be labeled node-role.kubernetes.io/master= and tainted node-role.kubernetes.io/master=:NoSchedule

Is there any change in kubo-deployment?
Yes (forthcoming), an ops file that will deploy CFCR with kubelets on the master.

Is there any change in kubo-ci?
Yes (forthcoming), to test this variant of CFCR deployment.

Does this affect upgrade, or is there any migration required?
No, though future capabilities that build on this may (e.g. pluggable CNIs).

Which issue(s) this PR fixes:
N/A

Release note:

[cfdreddbot]

✅ Hey svrc-pivotal! The commit authors and yourself have already signed the CLA.

[tvs]

This PR shouldn't be necessary - everything that's happening here can already be done as part of the existing k8s-args properties.

Taints can be registered using --register-with-taints and the labels can be added to --node-labels.

[svrc]

I’ve tried that, but I don’t believe kubelets can self-register themselves as a master with the `—node-labels` option, there’s only a small set of labels allowed: https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/apis/well_known_labels.go This is why Kubeadm for example does the labeling and tainting on its own and not via kubelet CLI option. `—register-with-taints` does work, but since we need to label these nodes via K8s CLI/API anyway, rather than splitting the labeling and tainting, I figured it was clearer to put them together in one place. Happy to remove that line here however if it is preferred.

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• ❌ Stu Charlton (01a899c)
• ❌ cfcr (6ed011f)