Handle unlimited ulimit

[subnetmarco]

Handle the ulimit value in the CLI when it's unlimited and not a numeric value.

[Tieske]

This sets/influences the values for; worker_rlimit_nofile and worker_connections.

should they be removed and left to the user to optimize (directly nginx config)?

[subnetmarco]

It seems like by default worker_rlimit_nofile sets the value of the ulimit, so we can avoid setting it explicitly. But worker_connections by default is 512 and that definitely needs to be increased.

[Tieske]

What is the proper value then?

imo 2 options;

1. we retain current behaviour, but explicitly need to set a number when its "unlimited"
2. only retain worker_connections and make it configurable in the config file