@Override
    public void handleRequestDone(Request request) {
        ActivateClusterStateVersionRequest.Reply reply = getReply(request);
        this.request.setReply(reply);
        waiter.done(this.request);
    }
Binds together the reply received for a particular cluster state activation RPC and
the cluster controller-internal callback handler which expects to receive it.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/rpc/RPCActivateClusterStateVersionWaiter.java