ArduCopter: set AUTO_YAW_HOLD when user control yaw during nogps land

ArduCopter/mode_land.cpp

@@ -102,6 +102,9 @@ void Copter::ModeLand::nogps_run()
 
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(channel_yaw->get_control_in());
+        if (!is_zero(target_yaw_rate)) {
+            auto_yaw.set_mode(AUTO_YAW_HOLD);
+        }
     }
 
     // disarm when the landing detector says we've landed