[Rspamd] Add stopsignal (testing)

data/Dockerfiles/rspamd/Dockerfile

@@ -24,4 +24,6 @@ COPY docker-entrypoint.sh /docker-entrypoint.sh
 
 ENTRYPOINT ["/docker-entrypoint.sh"]
 
+STOPSIGNAL SIGTERM
+
 CMD ["/usr/bin/rspamd", "-f", "-u", "_rspamd", "-g", "_rspamd"]