void addChild(Route route) {
        RoutingNode child = new RoutingNode(this, route);
        if (shouldIgnoreResult()) {
            child.route.getHop(0).setIgnoreResult(true);
        }
        children.add(child);
    }
Adds a child routing node to this based on a route. This is package private because client code should only
access it through a {@link RoutingPolicy} and its {@link RoutingContext#addChild(Route)} method.

@param route The route to store in the child node.
messagebus/src/main/java/com/yahoo/messagebus/routing/RoutingNode.java