Replace Vhost for VirtIO Vsock

[raduweiss]

Using vhost mean that there's one extra attack surface to deal with, and one less layer to apply mitigations to. We need to implement Vsockets without Vhost.

[raduweiss]

Closing this since we won't use Vhost anymore, for now.

[raduweiss]

Aaaand reopening :)

[dhrgit]

Moving discussion to #650 and closing this.