Nagios: Update plugin for defining hosts and host groups

This renames the check_update_prometheus_hosts plugin to be more
representative of what the current functionality does, which is
to simply define nagios hosts. This also updates the behavior of
the plugin to no longer force a reload of nagios via a hangup
signal when attempting to update the hosts file. The result is a
significant reduction in the logs output by the Nagios service,
which will better enable tracking history of service checks and
hosts.

Instead of this plugin being run as a recurring check, it can now
be run as an init container for the Nagios pod so Nagios has a
comprehensive list of its hosts and host groups before starting
the service

Change-Id: Ife2cdf2112db3798dbde73bafe436ef3c0c8a870
Signed-off-by: Steve Wilkerson <sw5822@att.com>

nagios/plugins/define-nagios-hosts.py

@@ -113,20 +113,6 @@ def update_config_file(object_file_loc):
 
     with open(object_file_loc, 'w+') as object_file:
         object_file.write("{} \n {}".format(nagios_hosts, nagios_hostgroups))
-    reload_nagios()
-
-
-def reload_nagios():
-    try:
-        # NOTE(srwilkers): We need the worker PIDs parent, which is the
-        # grandparent of the running process
-        worker_pid = os.getpid()
-        grandparent_pid = os.popen("ps -p %d -oppid=" % os.getppid()).read().strip()
-        os.kill(int(grandparent_pid), signal.SIGHUP)
-    except Exception as e:
-        print('Unable to reload Nagios with new host configuration')
-        print('Nagios worker PID: {}. Nagios worker grandparent PID: {}'.format(worker_pid, grandparent_pid))
-        sys.exit(NAGIOS_CRITICAL)
 
 
 def get_nagios_hostgroups(node_list):