Cleanup references to carthage.vm

[srak289]

No description provided.

[hartmans]

@srak289 I think that at least the tests need to enable the libvirt plugin. to succeed.

[srak289]

I'm not very familiar with how the tests are architected; should I move tests/test_vm.py to tests/test_libvirt.py ?
Looking through tests I'm not exactly sure where it would be appropriate to enable the libvirt plugin.

[hartmans]

Renaming to test_libvirt sounds good, although note you'd need to update github workflows.
Best activation would probably be to create a session scope fixture enable_libvirt_plugin in conftest.py and use that fixture in vm_image in conftest.py and the ainjector fixture in test_vm.py