Cleanup, handle error in req2param on flushCache

lib/cartodb/cartodb_windshaft.js

@@ -82,10 +82,10 @@ var CartodbWindshaft = function(serverOptions) {
     ws.del(serverOptions.base_url + '/flush_cache', function(req, res){
         ws.doCORS(res);
         Step(
-            function(){
+            function flushCache(){
                 serverOptions.flushCache(req, serverOptions.cache_enabled ? Cache : null, this);
             },
-            function(err, data){
+            function sendResponse(err, data){
                 if (err){
                     ws.sendError(res, {error: err.message}, 500, 'DELETE CACHE');
                     //res.send(500);

lib/cartodb/server_options.js

@@ -354,11 +354,17 @@ module.exports = function(){
         var that = this;
 
         Step(
-            function(){
+            function getParams(){
+                // this is mostly to compute req.params.dbname
                 that.req2params(req, this);
             },
-            function(err, data){
-                if (err) throw err;
+            function flushInternalCache(err){
+                // TODO: implement this, see
+                // http://github.com/Vizzuality/Windshaft-cartodb/issues/73
+                return true;
+            },
+            function flushVarnishCache(err){
+                if (err) { callback(err); return; }
                 if(Cache) {
                   Cache.invalidate_db(req.params.dbname, req.params.table);
                 }