Fix Multus version to stable in comac-in-a-box

Change-Id: If5fcbe8bb06ca3173128e36869d996a824be4d6c
diff --git a/comac-in-a-box/Makefile b/comac-in-a-box/Makefile
index 6e00854..bf536b2 100644
--- a/comac-in-a-box/Makefile
+++ b/comac-in-a-box/Makefile
@@ -90,7 +90,7 @@
 		-e "{'docker_version' : $(DOCKER_VERSION)}" \
 		-e "{'docker_iptables_enabled' : True}" \
 		-e "{'kube_version' : $(K8S_VERSION)}" \
-		-e "{'kube_network_plugin_multus' : True}" \
+		-e "{'kube_network_plugin_multus' : True, 'multus_version' : stable}" \
 		-e "{'kube_proxy_mode': iptables}" \
 		-e "{'kube_pods_subnet' : 192.168.0.0/17, 'kube_service_addresses' : 192.168.128.0/17}" \
 		-e "{'kube_apiserver_node_port_range' : 2000-36767}" \