Adopt dsync interface changes and major cleanup on RPC server/client.

* Rename GenericArgs to AuthRPCArgs
* Rename GenericReply to AuthRPCReply
* Remove authConfig.loginMethod and add authConfig.ServiceName
* Rename loginServer to AuthRPCServer
* Rename RPCLoginArgs to LoginRPCArgs
* Rename RPCLoginReply to LoginRPCReply
* Version and RequestTime are added to LoginRPCArgs and verified by
  server side, not client side.
* Fix data race in lockMaintainence loop.

cmd/auth-rpc-server.go

@@ -0,0 +1,43 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+// Base login method name.  It should be used along with service name.
+const loginMethodName = ".Login"
+
+// AuthRPCServer RPC server authenticates using JWT.
+type AuthRPCServer struct {
+}
+
+// Login - Handles JWT based RPC login.
+func (b AuthRPCServer) Login(args *LoginRPCArgs, reply *LoginRPCReply) error {
+	// Validate LoginRPCArgs
+	if err := args.IsValid(); err != nil {
+		return err
+	}
+
+	// Authenticate using JWT.
+	token, err := authenticateNode(args.Username, args.Password)
+	if err != nil {
+		return err
+	}
+
+	// Return the token.
+	reply.AuthToken = token
+
+	return nil
+}