Unify check for TF backend

Related-Prod: PRODX-37464
Change-Id: I39e7ac4b28207f705b54d7a7204894510f2f1045
diff --git a/neutron_tempest_plugin/api/test_timestamp.py b/neutron_tempest_plugin/api/test_timestamp.py
index 0cf28d5..c39c523 100644
--- a/neutron_tempest_plugin/api/test_timestamp.py
+++ b/neutron_tempest_plugin/api/test_timestamp.py
@@ -15,6 +15,7 @@
 
 from neutron_lib import constants
 from tempest.common import utils
+from tempest import config as tempestconf
 from tempest.lib.common.utils import data_utils
 from tempest.lib import decorators
 
@@ -306,7 +307,7 @@
             security_group['id'], name=security_group['name'] + 'new')[
                 'security_group']
         # Workaround for PRODX-7986
-        if CONF.service_available.contrail:
+        if tempestconf.is_tungstenfabric_backend_enabled():
             updated_security_group = self.client.show_security_group(
                 security_group['id'])['security_group']