kubernetes: 1.8 regression: Can't pull images from docker.io without explicit path on centos/fedora/rhel

https://github.com/kubernetes/kubernetes/pull/51751 bumped the vendored docker library and introduced a regression where pods with images that don’t contain an explicit “docker.io/” repo path result in ErrImagePull failures.

apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
  - name: busybox
    image: busybox
    command:
    - sleep
    - "100"
  terminationGracePeriodSeconds: 0
  restartPolicy: Never

Results in the following error:

Failed to pull image "busybox": rpc error: code = Unknown desc = no such image: "docker.io/library/busybox:latest"

Pod gets ErrImagePull

docker images shows that the image has been pulled, though not by that name

$ docker images | grep busybox
docker.io/busybox                                      latest              d20ae45477cb        2 weeks ago         1.13 MB

Changing the image to docker.io/busybox in the pod spec corrects the issue.

I think the new code that is changing the behavior is somewhere in here https://github.com/kubernetes/kubernetes/blob/master/vendor/github.com/docker/distribution/reference/normalize.go#L78-L98

familiarizeName() is a new function brought in by the bump.

If I checkout the commit before the bump, the problem does not occur.

@derekwaynecarr @DirectXMan12 @dashpole

related: https://bugzilla.redhat.com/show_bug.cgi?id=1496630