Server: Close fallback logging handler before removal to prevent leak

Signed-off-by: Pavel Kácha <ph@cesnet.cz>

warden3/warden_server/warden_server.py

@@ -148,6 +148,7 @@ def get_clean_root_logger(level=logging.INFO):
     logger = logging.getLogger(__name__)
     logger.setLevel(level)
     while logger.handlers:
+        logger.handlers[0].close()
         logger.removeHandler(logger.handlers[0])
     while logger.filters:
         logger.removeFilter(logger.filters[0])