Analagous problem to LMIC confirmed tx-status problem

[Terry Moore]

As part of mcci-catena/arduino-lmic@53c27e4, we added the following:

            // compute exit status
            if (ev == EV_TXCANCELED) {
                // canceled: unsuccessful.
                fSuccess = 0;
            } else if (/* ev == EV_TXCOMPLETE  && */ LMIC.pendTxConf) {
                fSuccess = (LMIC.txrxFlags & TXRX_ACK) != 0;
            } else {
                // unconfirmed uplinks are successful if they were sent.
                fSuccess = 1;
            }

Arduino_LoRaWAN doesn't have those checks (for confirmed/unconfirmed uplink, and cancel) and it should.