Give threads less time to shut down gracefully. Attempt shutdown() rather than stop() on the telnet connections to see if that improves things

providers/sigrefdata/file_download_sig_ref_data_provider.py

@@ -33,7 +33,7 @@ class FileDownloadSIGRefDataProvider(SIGRefDataProvider):
     def stop(self):
         super().stop()
         if self._thread:
-            self._thread.join(timeout=35)
+            self._thread.join(timeout=12)
             if self._thread.is_alive():
                 logger.warning(f"{self.sig_name} SIG ref data worker thread did not exit on time and will be killed.")