@Override
            public void handleStateConvergedInCluster(ClusterStateBundle states) {
                synchronized (monitor) {
                    currentState = convergedState = states.getBaselineClusterState();
                    monitor.notifyAll();
                }
            }
Return null if met, why not if it is not met.
clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/testutils/WaitCondition.java