Sets the kind of application, thus protocol, that will be spoken when transfering files to and from the guest.
Avocado-VT currently allows for two options: 'scp' or 'rss'.
For Linux VMs, we default to SSH:
variants: - @Linux: file_transfer_client = scp
And for Microsoft Windows VMs we default to rss:
variants: - @Windows: file_transfer_client = rss
No other documentation currently references this configuration key.