Recent busybox traceroute applet versions support both IPv4 and IPv6 and default to IPv6 when running a route trace to an IPv6 enabled target host. Pass the `-4` flag to enforce IPv4 mode in this case. Fixes: #5155 Signed-off-by: Jo-Philipp Wich <jo@mein.io> (cherry picked from commit c4f429461545d1401429e7ba133f24a55d1015b6)