[handler] Add second test in test suite + fix issue with ack check
[handler] Add second test in test suite + fix issue with ack check

TheThingsNetwork/ttn,mgranberry/ttn,mgranberry/ttn,TheThingsNetwork/ttn,TheThingsNetwork/ttn,LoRaWanSoFa/ttn,mgranberry/ttn,jvanmalder/ttn,LoRaWanSoFa/ttn,jvanmalder/ttn,jvanmalder/ttn