[router] Fix test issue with blocking channel
[router] Fix test issue with blocking channel

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