Support containerized kubelet in CI

* 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

cluster/images/hyperkube/Makefile

@@ -20,7 +20,7 @@
 REGISTRY?=staging-k8s.gcr.io
 ARCH?=amd64
 OUT_DIR?=_output
-HYPERKUBE_BIN?=$(OUT_DIR)/dockerized/bin/linux/$(ARCH)/hyperkube
+HYPERKUBE_BIN?=$(shell pwd)/../../../$(OUT_DIR)/dockerized/bin/linux/$(ARCH)/hyperkube
 
 BASEIMAGE=k8s.gcr.io/debian-hyperkube-base-$(ARCH):0.10
 TEMP_DIR:=$(shell mktemp -d -t hyperkubeXXXXXX)
@@ -33,7 +33,7 @@ ifndef VERSION
     $(error VERSION is undefined)
 endif
 	cp -r ./* ${TEMP_DIR}
-	cp ../../../${HYPERKUBE_BIN} ${TEMP_DIR}
+	cp ${HYPERKUBE_BIN} ${TEMP_DIR}
 
 	chmod a+rx ${TEMP_DIR}/hyperkube