fix an invalid use of dropChannel

lib/hk-util.js

@@ -144,7 +144,7 @@ const checkExpired = function (Env, Server, channel) {
             error: 'EEXPIRED',
             channel: channel
         }, Env.id);
-        dropChannel(channel);
+        dropChannel(Env, channel);
     });
 
     // return true to indicate that it has expired