[broker] Rename test functions + add comments to packet_test
[broker] Rename test functions + add comments to packet_test

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