private static String checkHttpSendDirective(String upstreamName) {
        return "check_http_send \"" +
               "GET /status.html HTTP/1.0\\r\\n" +
               "Host: " + upstreamName + "\\r\\n" +
               "\\r\\n\";";
    }
Converts a {@link RoutingTable} to Nginx's own config format.

@author Martin Polden
routing-generator/src/main/java/com/yahoo/vespa/hosted/routing/nginx/NginxConfig.java