public ClusterState getClusterState() {
        return Optional.ofNullable(getClusterStateBundle())
                .map(ClusterStateBundle::getBaselineClusterState)
                .orElse(null);
    }
Returns the latest system state version received, or empty if none are received yet.
clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/DummyVdsNode.java