Azure Stack support for Azure Backup

[Azure Stack operators](https://docs.microsoft.com/en-us/azure/azure-stack/azure-stack-key-features) can now back up and recover guest OS, data disks and volumes using [Azure Backup](https://azure.microsoft.com/en-us/services/backup/). This new ability gives operators more options when developing a backup strategy for Azure Stack. [Learn more](https://docs.microsoft.com/en-us/azure/azure-stack/azure-stack-backup-enable-backup-console) about Azure Stack backup. * Azure Stack * Features * [ Azure Stack](https://azure.microsoft.com/en-gb/overview/azure-stack/)