networkTests: IPv6 added to testGetRouteDeviceTo

Change-Id: I07371231ff8c57e6fc0a9bf66befc8b3430fd107
Signed-off-by: Petr Horáček <phoracek@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/32615
Reviewed-by: Dan Kenigsberg <danken@redhat.com>