nagios optimizations

Hi there,

this is one of the changes we did at T-Labs as mentioned in my [blog post](http://blog.hendrikvolkmer.de/2012/09/26/crowbar-at-scale/).

I rebased our changes to "release/fred/master" as of now.

Going forward with the Crowbar development we need a solution on how to include community cookbooks without changing them. The changes made to the nagios recipe would be applicable to the nagios community cookbook as well. If the cookbook would just have been included "by reference" e.g. using [librarian](https://github.com/applicationsonline/librarian) or [berkshelf](http://berkshelf.com/) I would have made these changes to the [source cookbook](http://community.opscode.com/cookbooks/nagios) and everyone (not only the Crowbar community) would be able to leverage these optimisations.

Cheers,
Hendrik