VM/VMSS create: clean up identity related information in the output

[yugangw-msft]

//CC: @tjprescott @derekbekoe, this simple change is to follow up with the feedback from identity team after they tried out the CLI
Not a hurry to get it in, but feel free to advise when it is the right time

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[azuresdkci]

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[tjprescott]

Due to recent changes to the CLI core, you will need to rebase your changes against the latest in the dev branch.

[yugangw-msft]

Closing as #5273 will cover this