fixed isolated instance query

* Was considering an isolated instance: any instance that has at least 1
group with no controller. This is technically correct since an iso node
can not be a part of a non-iso group.
* The query is now more robust and considers a node an iso node if ALL
groups that a node belong to ALL have a controller.
* Also added better debugging for the special tower instance group
* Added a check for the existance of the special tower group so that
logs are less "messy" during the install process.

awx/main/managers.py

@@ -114,7 +114,7 @@ class InstanceManager(models.Manager):
         return "tower"
 
     def all_non_isolated(self):
-        return self.filter(rampart_groups__controller__isnull=True).distinct()
+        return self.exclude(rampart_groups__controller__isnull=False)
 
 
 class InstanceGroupManager(models.Manager):

awx/main/models/ha.py

@@ -163,10 +163,6 @@ class InstanceGroup(models.Model, RelatedJobsMixin):
     def _get_related_jobs(self):
         return UnifiedJob.objects.filter(instance_group=self)
 
-    def add_all_non_iso_instances(self):
-        self.instances = Instance.objects.all_non_isolated()
-        self.save()
-
 
     class Meta:
         app_label = 'main'

awx/main/tasks.py

@@ -144,8 +144,16 @@ def apply_cluster_membership_policies(self):
         Group = namedtuple('Group', ['obj', 'instances'])
         Node = namedtuple('Instance', ['obj', 'groups'])
 
-        # Add every instnace to the special 'tower' group
-        InstanceGroup.objects.get(name='tower').add_all_non_iso_instances()
+        # Add every instance to the special 'tower' group
+        tower_q = InstanceGroup.objects.filter(name='tower')
+        if tower_q.exists():
+            tower_inst = tower_q[0]
+            tower_inst.instances = Instance.objects.all_non_isolated()
+            instances_hostnames = [i.hostname for i in tower_inst.instances.all()]
+            logger.info(six.text_type("Setting 'tower' group instances to {}").format(instances_hostnames))
+            tower_inst.save()
+        else:
+            logger.warn(six.text_type("Special 'tower' Instance Group not found."))
 
         # Process policy instance list first, these will represent manually managed instances
         # that will not go through automatic policy determination