kubernetes: bookend kubeadm-init with stamp files.

It is possible to get rebooted halfway through the init process, after key
files like `/etc/kubernetes/kubelet.conf` have been created but before full
cluster setup is complete or networking is applied.

Right now the idempotency of kubeadm (or backing out from this half-way state
and resuming the initialisation) is not something I have investigated. By
dropped stamps before and after at least the situation will be somewhat
detectable/diagnosable so the user can e.g. nuke their persistent disk and
start again.

Signed-off-by: Ian Campbell <ijc@docker.com>

projects/kubernetes/kubernetes/kubeadm-init.sh

@@ -1,5 +1,6 @@
 #!/bin/sh
 set -e
+touch /var/lib/kubeadm/.kubeadm-init.sh-started
 kubeadm init --skip-preflight-checks --kubernetes-version @KUBERNETES_VERSION@ $@
 for i in /etc/kubeadm/kube-system.init/*.yaml ; do
     if [ -e "$i" ] ; then
@@ -11,3 +12,4 @@ if [ -f /var/config/kubeadm/untaint-master ] ; then
     echo "Removing \"node-role.kubernetes.io/master\" taint from all nodes"
     kubectl taint nodes --all node-role.kubernetes.io/master-
 fi
+touch /var/lib/kubeadm/.kubeadm-init.sh-finished