Prevent kubeadm-aio being run as root.

Prevent duplicate docker mounts by disallowing root in kubeadm-aio.

Change-Id: I3e743a0d82e03b9d2ffb3af685c27dd15415ab81
Closes-Bug: #1711744

tools/kubeadm-aio/kubeadm-aio-launcher.sh

@@ -15,6 +15,12 @@
 #    under the License.
 set -xe
 
+# Exit if run as root
+if [[ $EUID -eq 0 ]]; then
+   echo "This script cannot be run as root" 1>&2
+   exit 1
+fi
+
 # Setup shared mounts for kubelet
 sudo mkdir -p /var/lib/kubelet
 sudo mount --bind /var/lib/kubelet /var/lib/kubelet
@@ -38,6 +44,7 @@ sudo rm -rfv \
 
 : ${KUBE_CNI:="calico"}
 : ${CNI_POD_CIDR:="192.168.0.0/16"}
+
 # Launch Container
 sudo docker run \
     -dt \
@@ -67,7 +74,7 @@ while true; do
   if [ -f ${HOME}/.kubeadm-aio/admin.conf ]; then
     READY="True"
   fi
-  [ $READY == "True" ] && break || true
+  [ "$READY" == "True" ] && break || true
   sleep 1
   now=$(date +%s)
   [ $now -gt $end ] && \