Compliance lib can lose the thread #441
Description
As always happens.... fix one bug and find another. Transmit delays are working and we can reduce the TX duty cycle in compliance; and that exposes a bug in the compliance library. If you get to LMIC_COMPLIANCE_FSMSTATE_TESTMODE while the LMIC is still busy doing an uplink (as will happen when MAC commands on port 0 are retransmitted during EU Cert test 1.5 test 15.12), the FSM will exit without making sure a timer will wake it up.
It would be more robust to have a timer that wakes up the compliance FSM every second no matter what; but we should avoid dropping the thread.