Update service client access test_dns_integration

This commit updates the Designate service client access to use the
tempest registry instead of clients added to the client manager.

Depends-On: https://review.opendev.org/c/openstack/designate-tempest-plugin/+/800280
Change-Id: Ie72e31e8e9081d305a5fb79ae6296546e29a0ee8
diff --git a/neutron_tempest_plugin/scenario/test_dns_integration.py b/neutron_tempest_plugin/scenario/test_dns_integration.py
index 79c0993..240a5a8 100644
--- a/neutron_tempest_plugin/scenario/test_dns_integration.py
+++ b/neutron_tempest_plugin/scenario/test_dns_integration.py
@@ -47,8 +47,7 @@
     @classmethod
     def setup_clients(cls):
         super(BaseDNSIntegrationTests, cls).setup_clients()
-        cls.dns_client = cls.os_tempest.zones_client
-        cls.query_client = cls.os_tempest.query_client
+        cls.dns_client = cls.os_tempest.dns_v2.ZonesClient()
         cls.query_client.build_timeout = 30
 
     @classmethod