[SCN REFACTOR] replace flash back snapshot and remove read snapshot session

deps/oblib/src/lib/signal/ob_signal_handlers.cpp

@@ -130,7 +130,9 @@ void close_socket_fd()
     }
     DLOG(INFO, "[CLOSEFD], close socket fd finish");
   }
-
+  if (NULL != dir) {
+    closedir(dir);
+  }
 }