land_detector: refactored helper method names

src/modules/land_detector/MulticopterLandDetector.h

@@ -124,9 +124,9 @@ private:
 
 	/* get control mode dependent pilot throttle threshold with which we should quit landed state and take off */
 	float _get_takeoff_throttle();
-	bool _get_position_lock_available();
-	bool _get_manual_control_present();
-	bool _get_minimal_thrust();
+	bool _has_position_lock();
+	bool _has_manual_control_present();
+	bool _has_minimal_thrust();
 };