Admin Lib: Implement Service API (#3426)

Three APIs were added to control a minio server

* NewAdminClient()
* ServiceStop()
* ServiceRestart()
* ServiceStatus()

pkg/madmin/api-error-response.go

@@ -0,0 +1,60 @@
+/*
+ * 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 madmin
+
+import "encoding/xml"
+
+/* **** SAMPLE ERROR RESPONSE ****
+<?xml version="1.0" encoding="UTF-8"?>
+<Error>
+   <Code>AccessDenied</Code>
+   <Message>Access Denied</Message>
+   <BucketName>bucketName</BucketName>
+   <Key>objectName</Key>
+   <RequestId>F19772218238A85A</RequestId>
+   <HostId>GuWkjyviSiGHizehqpmsD1ndz5NClSP19DOT+s2mv7gXGQ8/X1lhbDGiIJEXpGFD</HostId>
+</Error>
+*/
+
+// ErrorResponse - Is the typed error returned by all API operations.
+type ErrorResponse struct {
+	XMLName    xml.Name `xml:"Error" json:"-"`
+	Code       string
+	Message    string
+	BucketName string
+	Key        string
+	RequestID  string `xml:"RequestId"`
+	HostID     string `xml:"HostId"`
+
+	// Region where the bucket is located. This header is returned
+	// only in HEAD bucket and ListObjects response.
+	Region string
+}
+
+// Error - Returns HTTP error string
+func (e ErrorResponse) Error() string {
+	return e.Message
+}
+
+// ErrInvalidArgument - Invalid argument response.
+func ErrInvalidArgument(message string) error {
+	return ErrorResponse{
+		Code:      "InvalidArgument",
+		Message:   message,
+		RequestID: "minio",
+	}
+}