Nagios server changes for working baseline

- updated 3rd-party monitoring plugins
- minor fixes: suppress auth token display, add magic header
- set up the nagios server side of NRPE
- add a NTP test on all nodes
- move 3rd-party plugins to new NRPE module; NRPE module handles nagios clients' config while nagios module handles nagios server config
- set up the nagios server side of monitoring using our various OpenStack plugins