Fix missing usage of the xml neutron clients

This commit adds a conf check for a use of the neutron xml clients
which is outside of the network api tests. This is causing failures
when the neutron xml api is not available.

Change-Id: I51ca8c5ceb65d4ed07b17ed3c1895eeef1c54878
diff --git a/tempest/api/compute/servers/test_create_server.py b/tempest/api/compute/servers/test_create_server.py
index bc452aa..d954c01 100644
--- a/tempest/api/compute/servers/test_create_server.py
+++ b/tempest/api/compute/servers/test_create_server.py
@@ -128,6 +128,9 @@
     @testtools.skipUnless(CONF.service_available.neutron,
                           'Neutron service must be available.')
     def test_verify_multiple_nics_order(self):
+        if getattr(self, '_interface',
+                   None) == 'xml' and not CONF.network_feature_enabled.xml_api:
+            raise self.skipException('Neutron XML API is not enabled')
         # Verify that the networks order given at the server creation is
         # preserved within the server.
         name_net1 = data_utils.rand_name(self.__class__.__name__)