nginx shared folder is never created

Hi all!

Problem

The nginx config file is not accessible in the /shared volume. This is related to https://github.com/haiwen/seafile-docker/issues/219#issuecomment-631957421 as it would enable us to update the nginx config file ourselves.

When calling start.sh, the script creates shared folders:

and then calls generate_local_nginx_conf

which tries to move the nginx config file to the shared folder /shared/nginx and then tries to link it to /etc/

But the shared folder /shared/nginx is never created, so the moving and linking fails.

Create the folder /shared/nginx in start.py.

Thanks!