new feat: instantiate a new VM without NIC

##### ISSUE TYPE

* Feature Idea

##### COMPONENT NAME

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UI
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##### SUMMARY

I need to instantiate a new instance from an existing template without a network card, or at least with it disabled since it contains services that connects automatically to the net at startup. AFAIK the "New instance" functionality does not allow to launch an instance without a network interface.

Start with the UI's "New instance" flow and trace how it creates an instance from an existing template and configures network interfaces. Define done as allowing a new instance to start without a network card, or with its network interface disabled, and verify the behavior through the relevant UI or instance-creation tests.

Written by the indexing model from the issue text.