/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.
9bbd321fec