Add Etag for VMSS, VMSSVM and VM

[feiskyer]

What would you like to be added:

Add Etag for VMSS, VMSSVM and VM, so as to avoid overwriting them in case they are changed by other components.

Why is this needed:

[feiskyer]

/assign @mainred

[k8s-ci-robot]

@feiskyer: GitHub didn't allow me to assign the following users: mainred.

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In response to this:

/assign @mainred

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