Automatic merge from submit-queue (batch tested with PRs 50693, 50831, 47506, 49119, 50871)
kubeadm: Implement support for using images from CI builds
**What this PR does / why we need it**: Implements support for CI images in kubeadm
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixeskubernetes/kubeadm#337
**Special notes for your reviewer**:
**Release note**:
```release-note
- kubeadm now supports "ci/latest-1.8" or "ci-cross/latest-1.8" and similar labels.
```