Added ability to not manage nfs services.

jbeard -  Sorry for spamming you with changes to your modules today.  I needed one more feature and that is to not have puppet manage the nfs services.  This a little bit more added to this change and I was not able to test ubuntu.

I added in a default option in nfs::server for configonly = false,  if you set to true,  then the service definitions will be skipped over.  Not today,  but if you don't mind I'd also like to update the packages/services/files to include if !defined statements to make the module a little more forgiving.

Anyways,  take a look and see what you think.  tested on centos6 and all is good.  

    class { 'nfs::server':
      configonly => true
    }