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Support containerized kubelet in CI

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

  * Adjust hyperkube Makefile to allow HYPERKUBE_BIN to be
    specified from outside

  * new DOCKER_ROOT variable to specify --root-dir and associated
    volume for kubelet to know where docker directory lives

  * Save the docker logs when we kill the kubelet container

  * Allow customized image for dockerized kubelet and build a Default
    image if one is not specified

  We should allow a custom build using script we have:
  `VERSION="latest" REGISTRY="k8s.gcr.io" hack/dev-push-hyperkube.sh`

  to be used quickly using DOCKERIZE_KUBELET. To do this we remove the
  hard coded `k8s.gcr.io/kubelet` image and introduce a new environment
  variable `KUBELET_IMAGE`.

  Note that we are switching to hyperkube from kubelet as we have a quick
  and easy script to build hyperkube image and load it into local docker
  daemon. This reduces bad hacks like `docker tag
  k8s.gcr.io/hyperkube-amd64:<tag> k8s.gcr.io/kubelet:latest` being used
  by folks today (see 62057)

  * Better cope with PID 0 when running "docker inspect" to look for
    the process id for kubelet container


**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```