[simulators.gateway] Rewrite forwarder tests. Again ? .... yes.
[simulators.gateway] Rewrite forwarder tests. Again ? .... yes.

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