benchmark: move http_simple.js to http directory

PR-URL: https://github.com/nodejs/node/pull/7094
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

benchmark/http/cluster.js

@@ -11,7 +11,7 @@ if (cluster.isMaster) {
     c: [50, 500]
   });
 } else {
-  require('../http_simple.js');
+  require('./_http_simple.js');
 }
 
 function main(conf) {

benchmark/http/simple.js

@@ -12,7 +12,7 @@ var bench = common.createBenchmark(main, {
 
 function main(conf) {
   process.env.PORT = PORT;
-  var server = require('../http_simple.js');
+  var server = require('./_http_simple.js');
   setTimeout(function() {
     var path = '/' + conf.type + '/' + conf.length + '/' + conf.chunks;
     var args = ['-d', '10s', '-t', 8, '-c', conf.c];