LMIC_reset() doesn't reliably send EV_RESET

[terrillmoore]

In order to work around network issues, client software must always find out when LMIC_reset() has been called. EV_RESET is supposed to be this notification, but it's not guaranteed to arrive, because it's not issued by LMIC_reset() itself, but by a wrapper runReset() which only can happen from inside the LMIC. This is pretty inconvenient for clients.

We should move the notification upcall into LMIC_reset().