Move models for restrictions to cluster object

Since there are a couple of places where models for
restrictions is initialized, it's moved to cluster object.
Also, comments from previous commit
(Ibba7951968cbafd59fff0d516e74f9dd9e454edc) are fixed

It's refactoring bug is not needed.

Change-Id: Ic499a5deefb12740ebedc630b024dae0b4248ec5

cluster_upgrade/tests/test_validators.py

@@ -187,10 +187,14 @@ class TestNodeReassignNoReinstallValidator(tests_base.BaseCloneClusterTest):
             "reprovision": False,
             "roles": ['controller', 'compute'],
         })
-        msg = "^Role 'controller' in conflict with role 'compute'.$"
-        with self.assertRaisesRegexp(errors.InvalidData, msg):
+        with self.assertRaises(errors.InvalidData) as exc:
             self.validator.validate(data, self.dst_cluster)
 
+        self.assertEqual(
+            exc.exception.message,
+            "Role 'controller' in conflict with role 'compute'."
+        )
+
 
 class TestCopyVIPsValidator(base.BaseTestCase):
     validator = validators.CopyVIPsValidator