public static Result disallow(String reason) {
            return new Result(Action.DISALLOWED, reason);
        }
We want to check with the distributors to verify that it is safe to take down the storage node.
@param node the node to be checked
@param clusterStateVersion the cluster state we expect distributors to have
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java