Control the visibility and use of hop node Instances

- the list, detail, and health check API views should not include them
- the Instance-InstanceGroup association views should not allow them
  to be changed
- the ping view excludes them
- list_instances management command excludes them
- Instance.set_capacity_value sets hop nodes to 0 capacity
- TaskManager will exclude them from the nodes available for job execution
- TaskManager.reap_jobs_from_orphaned_instances will consider hop nodes
  to be an orphaned instance
- The apply_cluster_membership_policies task will not manipulate hop nodes
- get_broadcast_hosts will ignore hop nodes
- active_count also will ignore hop nodes

awx/api/views/root.py

@@ -149,7 +149,7 @@ class ApiV2PingView(APIView):
         response = {'ha': is_ha_environment(), 'version': get_awx_version(), 'active_node': settings.CLUSTER_HOST_ID, 'install_uuid': settings.INSTALL_UUID}
 
         response['instances'] = []
-        for instance in Instance.objects.all():
+        for instance in Instance.objects.exclude(node_type='hop'):
             response['instances'].append(
                 dict(
                     node=instance.hostname,