CORD-879 eliminate unnecessary import of Subscriber model

Change-Id: Iff973f8485a8bf3df47a558b10efdafb8b19dfc8
diff --git a/xos/models.py b/xos/models.py
index f3f9f2b..65ac70f 100644
--- a/xos/models.py
+++ b/xos/models.py
@@ -1,5 +1,5 @@
 from django.db import models
-from core.models import Service, PlCoreBase, Slice, Instance, Tenant, TenantWithContainer, Node, Image, User, Flavor, Subscriber, NetworkParameter, NetworkParameterType, Port, AddressPool
+from core.models import Service, PlCoreBase, Slice, Instance, Tenant, TenantWithContainer, Node, Image, User, Flavor, NetworkParameter, NetworkParameterType, Port, AddressPool
 from core.models.plcorebase import StrippedCharField
 import os
 from django.db import models, transaction