lxc conf from native: implement no network conversion
lxc from native: migrate veth network configuration

Some of the LXC configuration properties aren't migrated since they
would only cause problems in libvirt-lxc:
  lxc.network.ipv[46]: LXC driver doesn't setup IP address of guests
  lxc.network.name
lxc from native: convert phys network types to net hostdev devices
lxc from native: convert lxc.tty to console devices
lxc from native: convert macvlan network configuration