fix(cluster): avoid command.reject being overwritten twice

Author: luin

lib/cluster/index.js

@@ -409,7 +409,8 @@ Cluster.prototype.sendCommand = function (command, stream, node) {
   var targetSlot = node ? node.slot : command.getSlot();
   var ttl = {};
   var _this = this;
-  if (!node) {
+  if (!node && !command.__is_reject_overwritten) {
+    command.__is_reject_overwritten = true;
     var reject = command.reject;
     var partialTry = _.partial(tryConnection, true);
     command.reject = function (err) {