traceroute: fix setting router alert regression (#114)
traceroute: fix setting router alert regression (#114)

Fix regression introduced in 70ed4a00c21d35ff6d7e6843c075c670f656a9f3.
This has already been fixed upstream in a7a1181011d26ab8157e7ab84375eac82719b25f.
netsec-ethz/scion,netsec-ethz/scion,netsec-ethz/scion,netsec-ethz/scion