remove /cluster/kubeadm.sh and /test/cmd/kubeadm.sh

/cluster/kubeadm.sh is used to find the kubeadm binary.
This file is legacy and is removed.

Remove /test/cmd/kubeadm.sh. This file contains a function that is used
to build kubeadm and invoke "make test". Move the function contents
to hack/make-rules/test-cmd.cmd.

Stop sourcing /test/cmd/kubeadm.sh in /test/cmd/legacy-script.sh.

Also remove the --kubeadm-path invocation as this can be handled
with an env. variable directly.

hack/make-rules/test-cmd.sh

@@ -122,7 +122,15 @@ __EOF__
 WHAT=${WHAT:-}
 if [[ ${WHAT} == "" || ${WHAT} =~ .*kubeadm.* ]] ; then
   kube::log::status "Running kubeadm tests"  
-  run_kubeadm_tests
+
+  # build kubeadm
+  make all -C "${KUBE_ROOT}" WHAT=cmd/kubeadm
+  # unless the user sets KUBEADM_PATH, assume that "make all..." just built it
+  export KUBEADM_PATH="${KUBEADM_PATH:=$(kube::realpath "${KUBE_ROOT}")/_output/local/go/bin/kubeadm}"
+  # invoke the tests
+  make -C "${KUBE_ROOT}" test \
+    WHAT=k8s.io/kubernetes/cmd/kubeadm/test/cmd
+
   # if we ONLY want to run kubeadm, then exit here.
   if [[ ${WHAT} == "kubeadm" ]]; then
     kube::log::status "TESTS PASSED"