Enable stub_status for nginx

Currently if you want the Genetics Ark nginx container to be monitored by Prometheus, you have to edit the GA nginx.conf file after deployment. This is because by default, nginx doesn't expose its stub status endpoint of basic monitoring information.

For the next version, edit the nginx.conf to add this to the end:

# stub_status allows Prometheus monitoring
location /stub_status {
stub_status on;
}
}