CORD-1488 Update neutron-api charm to specify source of Neutron ONOS plugin

Change-Id: I63af2b6824274ea1832d8e55e495326e08b837f0
diff --git a/roles/juju-setup/templates/juju_config.yml.j2 b/roles/juju-setup/templates/juju_config.yml.j2
index 9e41347..cc2f1f8 100644
--- a/roles/juju-setup/templates/juju_config.yml.j2
+++ b/roles/juju-setup/templates/juju_config.yml.j2
@@ -31,6 +31,9 @@
   onos-vtn-port: 8182
   neutron-security-groups: "True"
   overlay-network-type: vxlan
+  {% if enable_dpdk -%}
+  onos-vtn-branch: cord-2.0-dpdk-kilo
+  {% endif %}
 
 neutron-openvswitch: {}