Automatic merge from submit-queue (batch tested with PRs 63272, 63782, 63715, 63811, 63803). 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>.

Refactor kubeadm config list-images

In preparation for creating a `kubeadm config images pull`
this commit refactors `kubeadm config list-images` into
`kubeadm config images list`.
Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

**What this PR does / why we need it**:
Prepares the `kubeadm config images` subcommand so we can add more functionality to it.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Related to kubernetes/kubeadm#812

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```