Tracker: fixed startup order of setting mavlink system ID

AntennaTracker/system.cpp

@@ -30,6 +30,8 @@ void Tracker::init_tracker()
 
     GCS_MAVLINK::set_dataflash(&DataFlash);
 
+    mavlink_system.sysid = g.sysid_this_mav;
+
     // initialise serial ports
     serial_manager.init();
 
@@ -56,8 +58,6 @@ void Tracker::init_tracker()
         gcs[i].set_snoop(mavlink_snoop_static);
     }
 
-    mavlink_system.sysid = g.sysid_this_mav;
-
 #if LOGGING_ENABLED == ENABLED
     log_init();
 #endif