Start-AzsDiskMigrationJob doesn't validate disks on run

As per process on https://docs.microsoft.com/en-us/azure-stack/operator/azure-stack-manage-storage-shares?view=azs-2108#to-migrate-managed-disks-using-powershell end users are required to create a get-azsdisk object when moving disks. Upon running the disk migration cmdlet seems to take what's in the object at face value up to and including refusing to migrate a disk due to it being "Attached" even though the disk was detached prior to making an object with the appropriate disks to move via get-azsdisk.
Expected behavior should fall in line with other PowerShell cmdlets in validating the data on run rather than assuming the arbitrary data from a cast object is correct in order to prevent issues due to stale data.

从 issue 中描述的 Start-AzsDiskMigrationJob 和 Get-AzSDisk 对象流程开始。使用对象创建后已变陈旧的磁盘数据重现迁移，然后验证 cmdlet 是否在执行时验证当前磁盘状态，并正确处理已分离的磁盘。

由索引模型根据 Issue 内容生成。