added preemptible flag in gcloud compute instance-templates create

cluster/gce/util.sh

@@ -398,6 +398,10 @@ function create-node-template {
   fi
 
   local attempt=1
+  local preemptible_minions=""
+  if [[ "${PREEMPTIBLE_MINION}" == "true" ]]; then
+    preemptible_minions="--preemptible --maintenance-policy TERMINATE"
+  fi  
   while true; do
     echo "Attempt ${attempt} to create ${1}" >&2
     if ! gcloud compute instance-templates create "$1" \
@@ -408,7 +412,7 @@ function create-node-template {
       --image-project="${MINION_IMAGE_PROJECT}" \
       --image "${MINION_IMAGE}" \
       --tags "${MINION_TAG}" \
-      --network "${NETWORK}" \
+      --network "${NETWORK}" ${preemptible_minions} \
       $2 \
       --can-ip-forward \
       --metadata-from-file "$3","$4" >&2; then