Adds port 9000 to list of unallowed ports

php-fpm will use 9000, so if you set http_port (or something else) to 9000 you'd get errors like:

```
STDERR: nginx: [emerg] bind() to 0.0.0.0:9000 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:9000 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:9000 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:9000 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:9000 failed (98: Address already in use)
nginx: [emerg] still could not bind()
```