ci/test-on-iotlab: set error precision to periph_timer_periodic
ci/test-on-iotlab: set error precision to periph_timer_periodic

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