[router] Rewrite listen tests to reflect new Adapter behavior
[router] Rewrite listen tests to reflect new Adapter behavior

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