Only update index file if file is flushed to disk

There's no point in indexing the file if it hasn't been synced to
disk. Any attempts to index the file will fail if the file still has an
open data block.

server/modules/routing/avrorouter/avro_file.c

@@ -886,7 +886,10 @@ void avro_flush_all_tables(AVRO_INSTANCE *router, enum avrorouter_file_op flush)
     }
 
     /** Update the GTID index */
-    avro_update_index(router);
+    if (flush == AVROROUTER_FLUSH)
+    {
+        avro_update_index(router);
+    }
 }
 
 /**