lets try this another way

inventory/inventory

@@ -1075,6 +1075,11 @@ fed-cloud15.cloud.fedoraproject.org
 #fed-cloud-ppc01.cloud.fedoraproject.org
 fed-cloud-ppc02.cloud.fedoraproject.org
 
+# Group for hosts we don't want to monitor with nagios.
+[nomonitor:children]
+newcloud-control
+newcloud-compute
+
 [newcloud:children]
 newcloud-control
 newcloud-compute

roles/nagios_server/templates/nagios/hostgroups/all.cfg.j2

@@ -2,11 +2,8 @@
 # All Servers and associated devices
 ###############
 ## {{ env }}
-
 {% for key, value in groups.iteritems() %}
-{% if groups[key] != [] %}
-{% for host in groups[key] %}
-{% if hostvars[host].nagios_Check_Services['monitor'] == true %}
+{% if groups[key] != [] and groups[key] != 'nomonitor' %}
 define hostgroup{
        hostgroup_name {{ key }}
        alias          {{ key }}
@@ -15,8 +12,6 @@ define hostgroup{
 }
 {% endif %}
 {% endfor %}
-{% endif %}
-{% endfor %}
 
 ## Services with minimal monitoring
 define hostgroup{