Skip nameserver propagation tests when no NS's in conf

Without having any nameservers configured, these tests give
a "false sense of security" that everything is working.

Change-Id: I819e2db70acf9e4e2502385bc4b20896442e11c0
diff --git a/designate_tempest_plugin/tests/scenario/v2/test_zones.py b/designate_tempest_plugin/tests/scenario/v2/test_zones.py
index 6ee479f..6c5bf0e 100644
--- a/designate_tempest_plugin/tests/scenario/v2/test_zones.py
+++ b/designate_tempest_plugin/tests/scenario/v2/test_zones.py
@@ -13,11 +13,13 @@
 # under the License.
 from oslo_log import log as logging
 from tempest import test
+from tempest import config
 from tempest.lib import exceptions as lib_exc
 
 from designate_tempest_plugin.tests import base
 from designate_tempest_plugin.common import waiters
 
+
 LOG = logging.getLogger(__name__)
 
 
@@ -84,6 +86,7 @@
 
     @test.attr(type='slow')
     @test.idempotent_id('ad8d1f5b-da66-46a0-bbee-14dc84a5d791')
+    @config.skip_unless_config('dns', 'nameservers')
     def test_zone_create_propagates_to_nameservers(self):
         LOG.info('Create a zone')
         _, zone = self.client.create_zone()
@@ -94,6 +97,7 @@
 
     @test.attr(type='slow')
     @test.idempotent_id('d13d3095-c78f-4aae-8fe3-a74ccc335c84')
+    @config.skip_unless_config('dns', 'nameservers')
     def test_zone_delete_propagates_to_nameservers(self):
         LOG.info('Create a zone')
         _, zone = self.client.create_zone()