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/AutoFollowMe/FlightTaskAutoFollowMe.cpp

@@ -42,8 +42,9 @@ using namespace matrix;
 
 bool FlightTaskAutoFollowMe::update()
 {
+	bool ret = FlightTaskAuto::update();
 	_position_setpoint = _target;
 	matrix::Vector2f vel_sp = _getTargetVelocityXY();
 	_velocity_setpoint = matrix::Vector3f(vel_sp(0), vel_sp(1), 0.0f);
-	return true;
-}
+	return ret;
+}