Plane: remove rally argument from Write_Rally - use singleton

ArduPlane/Log.cpp

@@ -300,7 +300,7 @@ void Plane::Log_Write_Vehicle_Startup_Messages()
     // only 200(?) bytes are guaranteed by AP_Logger
     Log_Write_Startup(TYPE_GROUNDSTART_MSG);
     logger.Write_Mode(control_mode, control_mode_reason);
-    logger.Write_Rally(rally);
+    logger.Write_Rally();
     ahrs.Log_Write_Home_And_Origin();
     gps.Write_AP_Logger_Log_Startup_messages();
 }