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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
```