[WIP] check for valid task before "finishing"
[WIP] Restore entire startup sequence

In order to get the initial flight-mode async code
working, the loop at the end of arbitrator_startup()
was disabled.  This code is now re-enabled, and invoked
from arbitrator_startup_cb() which is called when it's
flight_mode task is finished.
[WIP] add strict-flight-mode config