On the NIC hotplug instructions, the user is instructed to start the VM in case is not running.

I think that if the VM is not running - the hotplug / hotplug procedure is irrelevant - as from a user's perspective its better to just define what you want and start the VM over starting the VM and performing a hotplug / hot-unplug:
- Its simpler and faster.
- It doesn't consume the spare resources we keep to hotplugging NICs.
- It doesn't involve live migration.

4.20-4.15

100%

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Add a prerequisite for the VM to be running.

It would also enable us to remove the virtctl prerequisite for most versions (NIC hotplug / hotunplug are declarative since v4.15)