Add option to pass boot disk type to gce create (#1308)

net/scripts/gce-provider.sh

@@ -113,6 +113,7 @@ cloud_CreateInstances() {
   declare optionalBootDiskSize="$6"
   declare optionalStartupScript="$7"
   declare optionalAddress="$8"
+  declare optionalBootDiskType="$9"
 
   declare nodes
   if [[ $numNodes = 1 ]]; then
@@ -143,6 +144,11 @@ cloud_CreateInstances() {
       --metadata-from-file "startup-script=$optionalStartupScript"
     )
   fi
+  if [[ -n $optionalBootDiskType ]]; then
+    args+=(
+        --boot-disk-type "${optionalBootDiskType}"
+    )
+  fi
 
   if [[ -n $optionalAddress ]]; then
     [[ $numNodes = 1 ]] || {