Automatic merge from submit-queue (batch tested with PRs 48333, 48806, 49046)
kubeadm: Split out markmaster to its own phase
**What this PR does / why we need it**:
Splits out related and atomic code into its own phase that can be invokable easily from the CLI.
Makes the code much easier to read by not using recursion and `wait.InfinitePoll` _inside_ of a recursing function, etc.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
Fixes: https://github.com/kubernetes/kubeadm/issues/53
Part of this more long-term goal: https://github.com/kubernetes/kubeadm/issues/148
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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