[CORD-1505]
Support multiple external interface names on compute nodes managed by VTN

Change-Id: I01f21a778bba60f8f040d714e4b3ec776557af19
diff --git a/roles/compute-node-config/defaults/main.yml b/roles/compute-node-config/defaults/main.yml
index cfbaa76..b8fed3c 100644
--- a/roles/compute-node-config/defaults/main.yml
+++ b/roles/compute-node-config/defaults/main.yml
@@ -9,8 +9,10 @@
 head_cord_profile_dir: /opt/cord_profile
 
 # name of the external interface on compute nodes
-# `fabric` is default in R-CORD
-compute_external_interface: fabric
+# `fabric` is default in R-CORD, VTN adds it to `br-int`
+compute_external_interfaces:
+  - fabric
+  - br-int
 
 # service configs referenced here are likely located in cord-profile/templates
 # used in openstack-compute-vtn.yaml.j2, referencing network in management-net.yaml.j2