cfg template w/ @libdir fact

Upon testing your module with my CentOS & ubuntu environment, I found an issue w/ the generated config files on the former platform (pointing to /usr/lib/nagios instead of /usr/lib64/nagios).

Thankfully it seems that your pre-existing fact from params.pp plugs right in.

This is my first edit of someone's module (let alone my first public pull request), so here's hoping I'm not doing it wrong!