Increase gunicorn keep-alive timeout for AWS deployment

Suggested keepalive time is 1-5 seconds for standard deployment,
but it should be much higher for deployments behind a load
balancer. We are hoping this might resolve the SSLEOFErrors which
have been seen on the AWS deployment.  Traefik's keepalive time
is hard-coded to 90 seconds so we want gunicorn's to be longer than
that, so we set it to 100 s.

docker/supervisord-apache2.conf

@@ -6,7 +6,7 @@ redirect_stderr=true
 priority=3
 
 [program:gracedb]
-command=/usr/local/bin/gunicorn config.wsgi:application --reload --config /app/gracedb_project/config/gunicorn_config.py --error-logfile='-' --access-logfile='-'
+command=/usr/local/bin/gunicorn config.wsgi:application --reload --config /app/gracedb_project/config/gunicorn_config.py --error-logfile='-' --access-logfile='-' --keep-alive=100
 directory=/app/gracedb_project
 user=gracedb
 group=www-data