tools/zep_dispatch: basic dual-stack support
tools/zep_dispatch: basic dual-stack support

Murdock does not support IPv6 on link-local interfaces.
Therefore in order to being able to use ZEP dispatcher in automated tests
on CI, we have to add dual-stack support.

OlegHahm/RIOT,miri64/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kYc0o/RIOT,miri64/RIOT,ant9000/RIOT,ant9000/RIOT,miri64/RIOT,OlegHahm/RIOT,ant9000/RIOT,kYc0o/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,kaspar030/RIOT,kYc0o/RIOT,kaspar030/RIOT,kYc0o/RIOT,OlegHahm/RIOT,jasonatran/RIOT,kaspar030/RIOT,ant9000/RIOT,miri64/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,miri64/RIOT,kaspar030/RIOT,kYc0o/RIOT,jasonatran/RIOT