Good software, bad username in .spec

This is one of the basic packages I use in every large environment, for Nagios or Icinga monitoring and easy admin checking. Three are 3 small bugs:

* NRPE should have its own user, not share the “nagios” user. That causes confusion with ownership of configuration files and the “nagios” user itself.
* NRPE should have its config files in /etc/nrpe, not /etc/nagios. Again, this causes confusion with who manages the files in /etc/nagios and makes source control and package management much more awkward.
* The default location of “/usr/lib/nagios/plugins” should be set based on architecture. It’s /usr/lib64/nagios/plugins on most x86_64 systems.