COOK-2134: Correctly use nrpe vs. nagios-nrpe-server when necessary

This fixes a long standing bug where NRPE couldn't be stopped on RHEL
systems because the killproc uses the nagios-nrpe-server name.

NRPE is nrpe on RHEL based systems and on source installs, but Debian packages it as nagios-nrpe-server.  Previosly Chef assumed everything was nagios-nrpe-server, which didn't work.