The newly added virtio-net implementation needs to interact with TAP
interfaces and MAC addresses, which is the reason why it is easier
to rely on existing packages net_util and net_gen.
One more thing, both net_util and net_gen could be trimmed down,
based on using only the things we need from cloud-hypervisor.
Both net_util, net_gen and sys_util are based on Firecracker
commit d4a89cdc0bd2867f821e3678328dabad6dd8b767.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>