Identity V3: create_domain() must return a description field

There once was a situation where the `description` field was not
returned if a domain was created without a description. This is
not longer the case so adjust the assertions.

Change-Id: Ie201495b8701eb0977ae3404bcb95cd546336bd6
diff --git a/tempest/api/identity/admin/v3/test_domains.py b/tempest/api/identity/admin/v3/test_domains.py
index 86a5764..7cfca81 100644
--- a/tempest/api/identity/admin/v3/test_domains.py
+++ b/tempest/api/identity/admin/v3/test_domains.py
@@ -152,11 +152,7 @@
         self.addCleanup(self._delete_domain, domain['id'])
         self.assertIn('id', domain)
         expected_data = {'name': d_name, 'enabled': True}
-        # TODO(gmann): there is bug in keystone liberty version where
-        # description is not being returned if it is not being passed in
-        # request. Bug#1649245. Once bug is fixed then we can enable the below
-        # check.
-        # self.assertEqual('', domain['description'])
+        self.assertEqual('', domain['description'])
         self.assertDictContainsSubset(expected_data, domain)