private void rpc_storageConnect(Request req) {
        synchronized(timer) {
            log.log(Level.FINEST, () -> "Dummy node " + this + " got old type handle connect message.");
            req.returnValues().add(new Int32Value(0));
        }
    }
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