mc_pos_control/FlightTask: apply nit-pick review findings

src/lib/flight_tasks/tasks/FlightTask/FlightTask.cpp

@@ -164,7 +164,7 @@ void FlightTask::_evaluateVehicleLocalPosition()
 
 void FlightTask::_evaluateDistanceToGround()
 {
-	// Altitude above ground is by default just the negation of the current local position in D-direction.
+	// Altitude above ground is local z-position or altitude above home or distance sensor altitude depending on what's available
 	_dist_to_ground = -_position(2);
 
 	if (PX4_ISFINITE(_dist_to_bottom)) {

src/lib/flight_tasks/tasks/FlightTask/FlightTask.hpp

@@ -211,7 +211,7 @@ protected:
 	matrix::Vector3f _position; /**< current vehicle position */
 	matrix::Vector3f _velocity; /**< current vehicle velocity */
 	float _yaw = 0.f; /**< current vehicle yaw heading */
-	float _dist_to_bottom = 0.0f; /**< current height above ground level */
+	float _dist_to_bottom = 0.f; /**< current height above ground level */
 	float _dist_to_ground = 0.f; /**< equals _dist_to_bottom if valid, height above home otherwise */
 
 	/**