VOL-212, VOL-213: Added support for a kafka cluster within swarm

Amendment:
- Added reference to voltha-net network

Change-Id: Ia6beaa564325f531d09b93c46a8867139e78e63a
diff --git a/Makefile b/Makefile
index c308592..8129ff7 100644
--- a/Makefile
+++ b/Makefile
@@ -177,6 +177,7 @@
 	docker pull ubuntu:xenial
 	docker pull wurstmeister/kafka:latest
 	docker pull wurstmeister/zookeeper:latest
+	docker pull zookeeper:latest
 	docker pull nginx:latest
 	docker pull portainer/portainer:latest