Fix listens "extra"

[Deltik]

This fix prevents the following error if extra are used in a listens:

----------
          ID: haproxy.config
    Function: file.managed
        Name: /etc/haproxy/haproxy.cfg
      Result: False
     Comment: Unable to manage file: Jinja variable 'listerner' is undefined
     Started: 07:32:21.282751
    Duration: 241.105 ms
     Changes:   
----------

This fix also ensures line breaks are properly added if the extra is a list.

[aboe76]

thanks for this fix