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Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>. Kubeadm ha upgrade **What this PR does / why we need it**: This PR implements one of the actions defined by https://github.com/kubernetes/kubeadm/issues/751 (checklist form implementing HA in kubeadm). see [KEP 0015](https://github.com/kubernetes/community/blob/master/keps/sig-cluster-lifecycle/0015-kubeadm-join-master.md) for more context With this PR, kubeadm implements a new command `kubeadm upgrade node experimental-control-plane` that managed upgrade of control plane components on a secondary control plane instance. The entire workflow in case of HA clusters will be: - Upgrade the control plane - run `kubeadm upgrade apply` on a first control plane instance - run `kubeadm upgrade node experimental-control-plane` on secondary control plane instances - Upgrade nodes **Special notes for your reviewer**: /CC @timothysc @luxas @chuckha @kubernetes/sig-cluster-lifecycle-pr-reviews **Release note**: ``` kubeadm now has the `kubeadm upgrade node experimental-control-plane` command for upgrading secondary control plane instances created with `kubeadm join --experimental-control-plane`. ```