Add option for qubes-vm-update to wait till qubes shut down to terminate

[ben-grande]

The problem you're addressing (if any)

I want to script with qubes-vm-update due to Salt being unreliable. But qubes-vm-update finishes after it asks the target to shutdown without waiting. Then I have to make a while true loop to check if the qube is running or not.

If I ask for the template fedora-41 to be updated and then clone it, the clone can happen before the qube shuts down, having an old state.

The solution you'd like

qubes-vm-update --wait-shutdown

An option that does the same as qvm-shutdown --wait.

The value to a user and who that user might be

Be able to script:

qubes-vm-update --wait-shutdown --targets TEMPLATE
qvm-clone TEMPLATE ANOTHER_TEMPLATE

Without cloning an old state.

Completion criteria checklist

No response

[ben-grande]

Here is waits for shutdown:

/~https://github.com/QubesOS/qubes-core-admin-linux/blob/a4157299e3f357aed56d62dc5bedd6b85790f29a/vmupdate/vmupdate.py#L397-L411

But here it doesn't:

/~https://github.com/QubesOS/qubes-core-admin-linux/blob/a4157299e3f357aed56d62dc5bedd6b85790f29a/vmupdate/qube_connection.py#L96

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Then, is this a bug instead of a feature?