New-AzureRmVmss/Vm should support a custom image.

[sergey-shandar]

Description

VM currently partly support a custom image, see VHD.

URL to disk is a name (id?)

See https://review.docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/tutorial-use-custom-image-powershell?branch=pr-en-us-33477

Script/Steps for Reproduction

Module Version

Get-Module -Name AzureRM -ListAvailable

Environment Data

$PSVersionTable

Debug Output