pulling throttle low in flight turns out to be more common than thought. Removed clearing of takeoff_complete flag. This is still cleared during disarm which is automatic after 30 seconds of no throttle.

ArduCopter/ArduCopter.pde

@@ -1633,7 +1633,7 @@ void update_throttle_mode(void)
 
 			}else{
 				// we are on the ground
-				takeoff_complete = false;
+				//takeoff_complete = false;
 
 				// reset baro data if we are near home
 				if(home_distance < 400  || GPS_enabled == false){ // 4m from home