fix onQos2publish code & update comments

lib/client.js

@@ -535,26 +535,28 @@ Client.prototype.handleAuthorizePublish = function(err, success, packet) {
     packet.payload = success;
   }
 
-  var dopuback = function() {
-    // if qos2Puback, then if qos 2, don't just ignore the message, puback it
-    // by converting internally to qos 1.
-    // this fools mqtt.js into not holding all messages forever
-    if (packet.qos === 2){
-      switch(that.server.onQoS2publish){
-        case 'dropToQoS1':
-          packet.qos = 1;
-          break;
-        case 'disconnect':
-          if (!this._closed && !this._closing) {
-            that.close(null, "qos2 caused disconnect");
-          }
-          return;
-          break;
-        default:
-          break;
-      }
+  // Mosca does not support QoS2
+  // if onQoS2publish === 'dropToQoS1', don't just ignore QoS2 message, puback it
+  // by converting internally to qos 1.
+  // this fools mqtt.js into not holding all messages forever
+  // if onQoS2publish === 'disconnect', then break the client connection if QoS2
+  if (packet.qos === 2){
+    switch(that.server.onQoS2publish){
+      case 'dropToQoS1':
+        packet.qos = 1;
+        break;
+      case 'disconnect':
+        if (!this._closed && !this._closing) {
+          that.close(null, "qos2 caused disconnect");
+        }
+        return;
+        break;
+      default:
+        break;
     }
+  }
 
+  var dopuback = function() {
     if (packet.qos === 1 && !(that._closed || that._closing)) {
       that.connection.puback({
         messageId: packet.messageId