Reset database connection before reconnecting when updating export state

arkindex/documents/export/__init__.py

@@ -129,6 +129,7 @@ def update_state(corpus_export: CorpusExport, state: CorpusExportState):
         corpus_export.save()
     except (InterfaceError, OperationalError) as e:
         logger.warning(f"Database connection has been lost, retrying: {e}")
+        connections["default"].connection = None
         connections["default"].connect()
         corpus_export.refresh_from_db(using="default")
         corpus_export.state = state