[CORD-3008] Before removing OLT check that no subscribers are using it

Change-Id: I7f3d0f9d552a74a05c3f447cbb35b75f29595c87
diff --git a/xos/unittest.cfg b/xos/unittest.cfg
index 123cb69..426392e 100644
--- a/xos/unittest.cfg
+++ b/xos/unittest.cfg
@@ -5,3 +5,4 @@
                  steps
                  pull_steps
                  event_steps
+                 models