Rover: mode rtl loses duplicate calls to calc_lateral_acceleration

Also no need to call calc_nav_steer
no need to set throttle before entering hold

APMrover2/mode_rtl.cpp

@@ -23,10 +23,6 @@ void ModeRTL::update_navigation()
 {
     // no loitering around the wp with the rover, goes direct to the wp position
     if (rover.verify_RTL()) {
-        g2.motors.set_throttle(g.throttle_min.get());
         rover.set_mode(rover.mode_hold);
-    } else {
-        calc_lateral_acceleration();
-        calc_nav_steer();
     }
 }