FlightTask: Fix ekf2 reset race condition during task switch (#14692)

* FlightTask: Fix ekf2 reset race condition during task switch

During a loss of GPS data when using GPS as primary height source,
the height is reset to baro and the local position gets invalid at the
same time. This triggers a switch to altitude flight task and a setpoint
reset.
This combination of events had the effect to ignore the height reset,
the large sudden height error could create an abrupt change of altitude
or even a crash.
The ekf2 reset is now done at the beginning of each update call.

src/lib/flight_tasks/tasks/AutoMapper/FlightTaskAutoMapper.cpp

@@ -49,6 +49,7 @@ bool FlightTaskAutoMapper::activate(vehicle_local_position_setpoint_s last_setpo
 
 bool FlightTaskAutoMapper::update()
 {
+	bool ret = FlightTaskAuto::update();
 	// always reset constraints because they might change depending on the type
 	_setDefaultConstraints();
 
@@ -107,7 +108,7 @@ bool FlightTaskAutoMapper::update()
 	// update previous type
 	_type_previous = _type;
 
-	return true;
+	return ret;
 }
 
 void FlightTaskAutoMapper::_reset()