PowerCLI: Shut down a virtual machine, and wait for it to be fully shut down.

Stop-VMGuestAndWait.ps1

function Stop-VMGuestAndWait {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)][String]$VMName
    )
    Stop-VMGuest $VMName -Confirm:$false
    do {
        Start-Sleep -Seconds 1
        $VMStatus = (Get-VM $VMName).PowerState
    } while ($VMStatus -ne "PoweredOff")
}