Remove NRPE commands from Hiera

These have now been moved to base::nrpe, as the pdxcat/nrpe module does not
support including them in Hiera.
Move NRPE commands to base::nrpe

I originally thought that I could define NRPE commands in Hiera using the
pdxcat/nrpe command, but it turns out that I can't. Instead, I need to
create them in a separate manifest.

This does that.