Automatic merge from submit-queue. 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>.

Allow to use version labels in kubeadm upgrade apply command.

**What this PR does / why we need it**:

kubeadm upgrade apply now is able to utilize all possible combinations
of version argument, including labels (latest, stable-1.8, ci/latest-1.9)
as well as specific builds (v1.8.0-rc.1, ci/v1.9.0-alpha.1.123_01234567889)

As side effect, specifying exact build to deploy from CI area is now also
possible in kubeadm init command.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes kubernetes/kubeadm#451

**Special notes for your reviewer**:
cc @luxas 

**Release note**:
```release-note
- kubeadm init can now deploy exact build from CI area by specifying ID with "ci/" prefix. Example: "ci/v1.9.0-alpha.1.123+01234567889"
- kubeadm upgrade apply supports all standard ways of specifying version via labels. Examples: stable-1.8, latest-1.8, ci/latest-1.9 and similar.
```