Explicit db field for is_container_group

We now have Container Groups that dont require a credential.

awx/main/managers.py

@@ -144,7 +144,8 @@ class InstanceManager(models.Manager):
             from awx.main.management.commands.register_queue import RegisterQueue
             pod_ip = os.environ.get('MY_POD_IP')
             registered = self.register(ip_address=pod_ip)
-            RegisterQueue('tower', None, 100, 0, []).register()
+            is_container_group = settings.IS_K8S
+            RegisterQueue('tower', None, 100, 0, [], is_container_group).register()
             return registered
         else:
             return (False, self.me())