fix: more reliable gunicorn restart

killasgroup will ensure that all child processes die even if gunicorn
fails to do it. This isn't truly required because stopwaitsecs and
gunicorn graceful timeout work fine. In any case, if supervisor has to
send SIGKILL, it better send it to entire process group.

bench/config/templates/supervisor.conf

@@ -11,6 +11,7 @@ autorestart=true
 stdout_logfile={{ bench_dir }}/logs/web.log
 stderr_logfile={{ bench_dir }}/logs/web.error.log
 stopwaitsecs=40
+killasgroup=true
 user={{ user }}
 directory={{ sites_dir }}