fix conn shutdown when transfer restart

src/modules/collector/sys/funcs/clients.go

@@ -43,3 +43,9 @@ func (rcc *RpcClientContainer) Put(addr string, client *rpc.Client) bool {
 	rcc.M[addr] = client
 	return true
 }
+
+func (rcc *RpcClientContainer) Del(addr string) {
+	rcc.Lock()
+	defer rcc.Unlock()
+	delete(rcc.M, addr)
+}

src/modules/collector/sys/funcs/push.go

@@ -110,7 +110,7 @@ func rpcCall(addr string, items []*dataobj.MetricValue) (dataobj.TransferResp, e
 		return reply, fmt.Errorf("%s rpc call timeout", addr)
 	case err := <-done:
 		if err != nil {
-			rpcClients.Put(addr, nil)
+			rpcClients.Del(addr)
 			client.Close()
 			return reply, fmt.Errorf("%s rpc call done, but fail: %v", addr, err)
 		}