Disable server_tokens directive in NGINX

>Draft CIS Benchmark 1.1.10

## Description
By default NGINX will happily tell a user what version of NGINX is in use. This is valuable information to an attacker, and should be turned off by making use of the `server\_tokens` directive.

## Rationale
Potential attackers may check if your version of NGINX contains known vulnerabilities. Hiding the version will slow down and mitigate potential attackers.

## Remediation
To disable the `server\_tokens` directive, set if to `off` inside a `server` block in your `nginx.conf`: ``` server { ... server_tokens off; ... } ```

## Audit
In the NGINX configuration file `nginx.conf` ensure the `server\_tokens` directive is set to `off`. You can also check a 404 page provided by NGINX and see if it displays a version number.