bnsgeyer and rmackay9 contributed to these changes
make_safe_shut_down waits for spool down before disarming
remove use of attitude_control::set_throttle_out_unstabilized to consolidate logic between multicopters and tradhelis
These references were taken to make the breaking out of Modes in Copter.
A lot of other code has already caused these sorts of things to go away,
but these particular ones seem reasonable to fix by pointing the users
at the copter object directly.
