vhost: add a blank line at the end of the header template

[vincentbernat]

Without it, we get something like this:

  error_log             /var/log/nginx/my_error.log;  location / {
    root      /var/www/html;
  }

With this commit, we get this:

  error_log             /var/log/nginx/my_error.log;

  location / {
    root      /var/www/html;
  }