message: fix Contract ErrorResponse
diff: "description": "Error Field contract."
  },
  "ErrorResponse": {
  + "properties": {
  + "error" : {
  + "x-ms-client-flatten": true,
  + "$ref": "#/definitions/ErrorResponseBody",
  + "description": "Properties of the Error Response."
  + }
  + },
  + "description": "Error Response."
  + },
  + "ErrorResponseBody": {
  "properties": {
  "code": {
  "type": "string",
  