network2 removed.

Follow up on #62.
vagrant-ibvirt by itself allows to set static IPs on VMs by supplying
`config.vm.ip = '1.2.3.4'` parameter.
Thus, with Libvirt DHCP disabled, and supplying own IPs to each VM, we
can have a decent working setup.
Furthermore, /etc/hosts approach is completely fine here for name
resolving purposes - neither of other approaches provide a flexibility
of a plain text file. With Vagrant We're not intended to build a working root DNS
servers setup and put it to production anyways :)