Add uWSGI `die-on-term` flag (#3429)

dockerfiles/uwsgi.ini

@@ -42,6 +42,10 @@ buffer-size = 8192
 # See https://github.com/searx/searx-docker/issues/24
 add-header = Connection: close
 
+# Follow SIGTERM convention
+# See https://github.com/searxng/searxng/issues/3427
+die-on-term
+
 # uwsgi serves the static files
 static-map = /static=/usr/local/searxng/searx/static
 # expires set to one day