- currently triggered via param COM_DO_CS_CHECK. ultimately this will
be replaced by a mavlink cmd
- new VehicleStatus.nav_state, NAVIGATION_STATE_CS_PREFLIGHT_CHECK.
this is how commander tells ControlAllocator to conduct the check
- (todo) within ControlAllocator we overwrite torque setpoints to do
the check. additionally we can also control servos directly from
there, in a different mode if that is needed.