public void setRequest(RPCActivateClusterStateVersionRequest request) {
        this.request = 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