Automatic merge from submit-queue
kubeadm: Migrate to client-go
**What this PR does / why we need it**: Finish the migration for kubeadm to use client-go wherever possible
**Which issue this PR fixes**: fixes #https://github.com/kubernetes/kubeadm/issues/52
**Special notes for your reviewer**: /cc @luxas @pires
**Release note**:
```release-note
NONE
```