fix network unit test case

Since neutron code bases was changed because of bug fix [1], network unit
test for the Tricircle has to be updated becuase of dependencies.

For More Detail:
neutron/db/ipam_backend_mixin.py

[1]https://review.openstack.org/#/c/288774/

Change-Id: I1142bdd75c1dd5d240d1d256d9687c2fe54612c8

tricircle/tests/unit/network/test_plugin.py

@@ -19,6 +19,7 @@ import mock
 from mock import patch
 import unittest
 
+from sqlalchemy.orm import attributes
 from sqlalchemy.orm import exc
 from sqlalchemy.sql import elements
 
@@ -499,6 +500,8 @@ class FakeSession(object):
         return FakeSession.WithWrapper()
 
     def query(self, model):
+        if isinstance(model, attributes.InstrumentedAttribute):
+            model = model.class_
         if model.__tablename__ not in RES_MAP:
             return FakeQuery([], model.__tablename__)
         return FakeQuery(RES_MAP[model.__tablename__],