Automatic merge from submit-queue
kubeadm: add api validation exit code
**What this PR does / why we need it**: This will help with automation and provide more meaningful exit code for api validation.
WIP to add more meaningful exit codes https://github.com/kubernetes/kubeadm/issues/61
This is a continuation from https://github.com/kubernetes/kubernetes/pull/42825 since it had to be closed.
**Special notes for your reviewer**: /cc @luxas
**Release note**:
```release-note
NONE
```
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