修复memcached incr的错误

@@ -29,6 +29,8 @@ module.exports = (limiter, policy) => {
 
     const key = `pc:limiter:${limiter.remoteIp}`;
 
+    let isNew = false;
+
     res.on('render', function() {
         let route = req.route ? req.route.path : '';
         let appPath = req.app.mountpath;
@@ -44,7 +46,7 @@ module.exports = (limiter, policy) => {
             pageIncr = 5;
         }
 
-        if (pageIncr > 0) {
+        if (pageIncr > 0 && !isNew) {
             cache.incrAsync(key, pageIncr);
         }
     });
@@ -70,6 +72,7 @@ module.exports = (limiter, policy) => {
             }
         } else {
             cache.setAsync(key, 1, 60);  // 设置key，1m失效
+            isNew = true;
             return Promise.resolve(true);
         }
     });