net/gcoap: make use of coap_opt_add_path()
net/gcoap: make use of coap_opt_add_path()

yogo1212/RIOT,kaspar030/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,ant9000/RIOT,RIOT-OS/RIOT,ant9000/RIOT,kYc0o/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,jasonatran/RIOT,basilfx/RIOT,OlegHahm/RIOT,ant9000/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,basilfx/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,kYc0o/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,OTAkeys/RIOT,miri64/RIOT,miri64/RIOT,authmillenon/RIOT,yogo1212/RIOT,miri64/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kaspar030/RIOT,miri64/RIOT,yogo1212/RIOT,miri64/RIOT,ant9000/RIOT,basilfx/RIOT,jasonatran/RIOT,yogo1212/RIOT,authmillenon/RIOT,authmillenon/RIOT,basilfx/RIOT,kaspar030/RIOT,ant9000/RIOT,authmillenon/RIOT,kYc0o/RIOT,OlegHahm/RIOT,jasonatran/RIOT,basilfx/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,kaspar030/RIOT,yogo1212/RIOT,jasonatran/RIOT,OlegHahm/RIOT