Rover: fix RC init order to avoid error message

Rover/system.cpp

@@ -130,8 +130,8 @@ void Rover::init_ardupilot()
     set_mode(*initial_mode, ModeReason::INITIALISED);
 
     // initialise rc channels
-    rc().init();
     rc().convert_options(RC_Channel::AUX_FUNC::ARMDISARM_UNUSED, RC_Channel::AUX_FUNC::ARMDISARM);
+    rc().init();
 
     rover.g2.sailboat.init();