Add -i node_key

Change-Id: I98799033f590a5addb7b70f3efd0582341d1fa51
(cherry picked from commit 2dfa9f522e8d184f7a2f984830894119e504f684)
diff --git a/cord-pod/make-vtn-external-yaml.sh b/cord-pod/make-vtn-external-yaml.sh
index d52c862..5a3fd18 100644
--- a/cord-pod/make-vtn-external-yaml.sh
+++ b/cord-pod/make-vtn-external-yaml.sh
@@ -47,7 +47,7 @@
     echo $NODE
     BRIDGE_ID=$(printf "of:%016d" $BRIDGE_IDX )
     BRIDGE_IDX=$(expr $BRIDGE_IDX + 1)
-    FIP=$(ssh -o StrictHostKeyChecking=no $NODE ip -4 addr show fabric 2> /dev/null | grep inet | awk '{print $2}')
+    FIP=$(ssh -i node_key -o StrictHostKeyChecking=no $NODE ip -4 addr show fabric 2> /dev/null | grep inet | awk '{print $2}')
     if [ -z "$FIP" ]
     then
       # Single-node POD case