Automatic merge from submit-queue (batch tested with PRs 41857, 41864, 40522, 41835, 41991)
kubeadm: Use a new label for marking and tainting the master node
**What this PR does / why we need it**:
Implements https://github.com/kubernetes/kubernetes/pull/39112 for kubeadm until that PR is merged. I want to proceed on this stuff, it has been pending for too long already.
It's at least pretty safe to apply this for kubeadm now, since we're still in alpha in v1.6 implementation-wise, only the CLI will be beta.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
Switch to the `node-role.kubernetes.io/master` label for marking and tainting the master node in kubeadm
```
cc @deads2k @liggitt @smarterclayton @jbeda @roberthbailey @mikedanese @justinsb @sttts @kubernetes/api-approvers @kubernetes/api-reviewers
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