Tracker: fix return results from preflight calibration

Was always returning success even in cases where it failed
Issue found by Coverity

AntennaTracker/GCS_Mavlink.cpp

@@ -580,9 +580,11 @@ void GCS_MAVLINK_Tracker::handleMessage(mavlink_message_t* msg)
                     tracker.init_barometer(false);
                     // zero the altitude difference on next baro update
                     tracker.nav_status.need_altitude_calibration = true;
+                    result = MAV_RESULT_ACCEPTED;
                 }
                 if (is_equal(packet.param4,1.0f)) {
                     // Can't trim radio
+                    result = MAV_RESULT_UNSUPPORTED;
                 } else if (is_equal(packet.param5,1.0f)) {
                     result = MAV_RESULT_ACCEPTED;
                     // start with gyro calibration
@@ -609,7 +611,6 @@ void GCS_MAVLINK_Tracker::handleMessage(mavlink_message_t* msg)
                         result = MAV_RESULT_FAILED;
                     }
                 }
-                result = MAV_RESULT_ACCEPTED;
                 break;
             }