pyroute2: IPv6 support

IPv6 support added to pyroute2 configurator.

Change-Id: I4f6cb4542d1de107aba7a92d65b744290f8a9583
Signed-off-by: Petr Horáček <phoracek@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/32033
Reviewed-by: Ondřej Svoboda <osvoboda@redhat.com>
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>