[MEDIUM] add a '%S' conversion specifier, it is a string that DO NOT represent an IP or subnet

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
[TEST] test "ip route 1.1.1.1 (device )? IP parsing

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
[FIXME] note a fixme, no real idea on how to fix it (or if it is worth fixing)

Signed-off-by: etienne basset <etienne.basset@numericable.fr>