Tracker: rename system_status as it won't be called from base class

AntennaTracker/GCS_Mavlink.cpp

@@ -67,7 +67,7 @@ uint32_t GCS_Tracker::custom_mode() const
     return tracker.control_mode;
 }
 
-MAV_STATE GCS_MAVLINK_Tracker::system_status() const
+MAV_STATE GCS_MAVLINK_Tracker::vehicle_system_status() const
 {
     if (tracker.control_mode == INITIALISING) {
         return MAV_STATE_CALIBRATING;

AntennaTracker/GCS_Mavlink.h

@@ -42,7 +42,7 @@ private:
     void send_global_position_int() override;
 
     MAV_MODE base_mode() const override;
-    MAV_STATE system_status() const override;
+    MAV_STATE vehicle_system_status() const override;
 
     bool waypoint_receiving;
 };