This simplifies capturing traffic with Wireshark on the host as each of
the guest's interfaces is clearly identified.
The three bridges were previously numbered starting from 0, this scheme
is restored here.
Guest and network configuration is setup using the libvirt
virtualization API. The [start|stop]_testing scripts have been updated
accordingly.
qemu/KVM does not currently support a hostfs, so the shared build tree
mount has been dropped for now.