Automatic merge from submit-queue (batch tested with PRs 63969, 63902, 63689, 63973, 63978). 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>.
Add a 'kubeadm config print-default' command
**What this PR does / why we need it**:
Improves the UX around creating config files.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes https://github.com/kubernetes/kubeadm/issues/829
**Special notes for your reviewer**:
**Release note**:
```release-note
kubeadm: A `kubeadm config print-default` command has now been added that you can use as a starting point when writing your own kubeadm configuration files
```
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