Implement stats middleware removing some duplicated code

lib/cartodb/middleware/error-middleware.js

@@ -35,8 +35,6 @@ module.exports = function errorMiddleware (/* options */) {
             res.set('X-Served-By-DB-Host', res.locals.dbhost);
         }
 
-        res.set('X-Tiler-Profiler', req.profiler.toJSONString());
-
         res.status(statusCode);
 
         if (req.query && req.query.callback) {
@@ -44,14 +42,6 @@ module.exports = function errorMiddleware (/* options */) {
         } else {
             res.json(errorResponseBody);
         }
-
-        try {
-            // May throw due to dns, see
-            // See http://github.com/CartoDB/Windshaft/issues/166
-            req.profiler.sendStats();
-        } catch (err) {
-            debug("error sending profiling stats: " + err);
-        }
     };
 };