netinfo: remove code duplication between nics, bridges, bonds and vlans

Change-Id: I7c54801822d487bde7f0e4ba9e79bf278e2a7598
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/24174
Reviewed-by: Dan Kenigsberg <danken@redhat.com>