Add support for directly managing instance groups

* Associating/Disassociating an instance with a group
* Triggering a topology rebuild on that change
* Force rabbitmq cleanup of offline nodes
* Automatically check for dependent service startup
* Fetch and set hostname for celery so it doesn't clobber other
  celeries
* Rely on celery init signals to dyanmically set listen queues
* Removing old total_capacity instance manager property

awx/main/managers.py

@@ -93,11 +93,6 @@ class InstanceManager(models.Manager):
         """Return count of active Tower nodes for licensing."""
         return self.all().count()
 
-    def total_capacity(self):
-        sumval = self.filter(modified__gte=now() - timedelta(seconds=settings.AWX_ACTIVE_NODE_TIME)) \
-                     .aggregate(total_capacity=Sum('capacity'))['total_capacity']
-        return max(50, sumval)
-
     def my_role(self):
         # NOTE: TODO: Likely to repurpose this once standalone ramparts are a thing
         return "tower"