message: updated OS Upgrade History API
diff: ],
  "description": "The Virtual Machine Scale Set List Skus operation response."
  },
  + "RollbackStatusInfo": {
  + "properties":{
  + "successfullyRolledbackInstanceCount" : {
  + "readOnly": true,
  + "type": "integer",
  + "format": "int32",
  + "description": "The number of instances which have been successfully rolled back."
  + },
  + "failedRolledbackInstanceCount" : {
  + "readOnly": true,
  + "type": "integer",
  + "format": "int32",
  + "description": "The number of instances which failed to rollback."
  + },
  + "rollbackError" : {
  + "$ref": "#/definitions/ApiError",
  + "readOnly": true,
  + "description": "Error Details if OS rollback failed."
  + }
  + },
  + "description": "Information about rollback on failed VM instances after a OS Upgrade operation"
  + },
  "UpgradeOperationHistoryStatus": {
  "properties": {
  "code": {
  "$ref": "#/definitions/ImageReference",
  "readOnly": true,
  "description": "Image Reference details"
  + },
  + "rollbackInfo": {
  + "$ref": "#/definitions/RollbackStatusInfo",
  + "readOnly": true,
  + "description": "Information about OS rollback if performed"
  }
  },
  "description": "Describes each OS upgrade on the Virtual Machine Scale Set."
  