Track the length of the client pending output buffers (still to transfer) in a new field in the client structure.

src/aof.c

@@ -295,6 +295,7 @@ struct redisClient *createFakeClient(void) {
      * so that Redis will not try to send replies to this client. */
     c->replstate = REDIS_REPL_WAIT_BGSAVE_START;
     c->reply = listCreate();
+    c->reply_bytes = 0;
     c->watched_keys = listCreate();
     listSetFreeMethod(c->reply,decrRefCount);
     listSetDupMethod(c->reply,dupClientReplyValue);