Automatic merge from submit-queue (batch tested with PRs 53783, 53175). 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: add Priority to admission control
**What this PR does / why we need it**:
Adds Priority admission control to kubeadm for all kubernetes versions > v1.9 alpha.
Related: https://github.com/kubernetes/kubernetes/pull/49322
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*:
fixes https://github.com/kubernetes/kubeadm/issues/434
**Special notes for your reviewer**:
**Release note**:
```release-note
Enable Priority admission control in kubeadm.
```
cc @luxas
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