Set db_url to correct endpoint for a single world

cake/benchmark_config

@@ -4,7 +4,7 @@
     "default": {
       "setup_file": "setup",
       "json_url": "/json.json",
-      "db_url": "/world.json",
+      "db_url": "/world/index.json",
       "query_url": "/world.json?queries=",
       "fortunes_url": "/fortunes",
       "plaintext_url": "/plaintext",
@@ -24,4 +24,4 @@
       "versus": "php"
     }
   }]
-}
+}