private NodeData getOrCreate(String nodeName, TreeMap<String, NodeData> nodes) {
            NodeData data = nodes.get(nodeName);
            if (data != null)
                return data;
            data = new NodeData();
            data.hostname = "127.0.0.1";
            nodes.put(nodeName, data);
            return data;
        }
Add a new trogdor agent node to the cluster.
trogdor/src/test/java/org/apache/kafka/trogdor/common/MiniTrogdorCluster.java