1.优化CALL Rpc错误返回

2.优化不同邻居Master服务发现规则

cluster/cluster.go

@@ -150,6 +150,7 @@ func (cls *Cluster) delServiceNode(serviceName string,nodeId int){
 	}
 }
 
+
 func (cls *Cluster) serviceDiscoverySetNodeInfo (nodeInfo *NodeInfo){
 	//本地结点不加入
 	if nodeInfo.NodeId == cls.localNodeInfo.NodeId {
@@ -272,6 +273,10 @@ func (cls *Cluster) GetMasterDiscoveryNodeInfo(nodeId int)  *NodeInfo{
 	return nil
 }
 
+func (cls *Cluster) IsMasterDiscoveryNode() bool{
+	return cls.GetMasterDiscoveryNodeInfo(cls.GetLocalNodeInfo().NodeId)!=nil
+}
+
 func (cls *Cluster) SetupServiceDiscovery(localNodeId int,setupServiceFun SetupServiceFun) {
 	if cls.serviceDiscovery!=nil {
 		return