Fix setting interface name in network metadata

Related-Prod: PRODX-3456
Change-Id: Ief2c4f950500ad3b06a97bc1625947120518115b
diff --git a/de/heat-templates/scripts/instance_boot.sh b/de/heat-templates/scripts/instance_boot.sh
index 76061dc..7ac054a 100644
--- a/de/heat-templates/scripts/instance_boot.sh
+++ b/de/heat-templates/scripts/instance_boot.sh
@@ -575,7 +575,7 @@
     ip=${TUNNEL_INTERFACE_IP}/${TUNNEL_INTERFACE_NETWORK_NETMASK}
 
     cat << EOF > ${if_metadata_file}
-${interface}:
+${TUNNEL_INTERFACE}:
   pci_id: "${pci_id}"
   ip_addr: "${ip}"
   mac: "${mac}"