fix nmcli_shows_correct_routes test
This test does not work if eth0 uses IPv6 (then nmcli shows ff00::/8 for eth0, which is not visible via ip command). Also, ip command shows dev lo IPv6 route, so this is why test worked if exactly one interface had IPv6.
This fix excludes "dev lo" and "ff00::/8" from counting.
@RunTests:nmcli_shows_correct_routes