Remove the kubelet container as it's unmaintained

cluster/images/kubelet/Dockerfile

-# Copyright 2016 The Kubernetes Authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-FROM centos
-ADD kubelet /kubelet
-RUN chmod a+rx /kubelet
-RUN cp /usr/bin/nsenter /nsenter
-
-VOLUME /var/lib/docker
-VOLUME /var/lib/kubelet
-CMD [ "/kubelet" ]

cluster/images/kubelet/Makefile

-# Copyright 2016 The Kubernetes Authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# build the kubelet image.
-
-# TODO: figure out the best base image
-# TODO: figure out how to best source the nsenter binary, if necessary
-# TODO: figure out how to make a single source of version info for these
-#       images
-VERSION=v0.16
-BIN_DIR=bin/linux/amd64
-LOCAL_OUTPUT_DIR=../../../_output/local
-
-release: clean
-	curl -O https://storage.googleapis.com/kubernetes-release/release/${VERSION}/${BIN_DIR}/kubelet
-	docker build -t gcr.io/google_containers/kubelet:${VERSION} .
-	gcloud docker push gcr.io/google_containers/kubelet:${VERSION}
-
-local: clean
-	cp ${LOCAL_OUTPUT_DIR}/${BIN_DIR}/kubelet .
-	docker build -t gcr.io/google_containers/kubelet .
-
-clean:
-	rm -f kubelet
-
-.PHONY: release