update recv failed err is nil

nm/start.go

@@ -202,7 +202,7 @@ func monitorWorker(op *operate.DockerOp) {
 					rev, err := worker.Recv()
 					if int64(sub) > conf.GetConfig().HeartRespTimeSecond || err != nil {
 						log.Error("Rev failed:", err)
-						params := buildParams(fmt.Sprintf("Rev failed:%s", err.Error()))
+						params := buildParams(fmt.Sprint("Rev failed:", err))
 						msgRespWorker.RegisterMsgResp(nodeManager, worker, GoodbyeResp, params)
 						nodeManager.UpdateStatus(false)
 						log.Error("Node manager heartbeat is over")