Copter: limit ATC_MOT_MIX_MAX in case of a fly away

ArduCopter/land_detector.cpp

@@ -176,7 +176,7 @@ void Copter::update_throttle_thr_mix()
         bool descent_not_demanded = pos_control->get_desired_velocity().z >= 0.0f;
 
         if ( large_angle_request || large_angle_error || accel_moving || descent_not_demanded) {
-            attitude_control->set_throttle_mix_max();
+            attitude_control->set_throttle_mix_max(pos_control->get_vel_z_control_ratio());
         } else {
             attitude_control->set_throttle_mix_min();
         }