Automatic merge from submit-queue (batch tested with PRs 57536, 63812). 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: Contact the kubelet on its healthz port instead of its readonly port
**What this PR does / why we need it**:
In order for us to disable the kubelet's readonly port in v1.11 (https://github.com/kubernetes/kubeadm/issues/732), we need to cut the dependency on that port being open. Instead, we can use the dedicated healthz port (using the defaults `--healthz-bind-address=127.0.0.1` and `--healthz-port=10248`, xref: https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/)
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Part of https://github.com/kubernetes/kubeadm/issues/732
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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