identity v3 token

Adds a test where get a token using identity api v3,
and use that to perform an operation using compute api.

Fixes bug 1161633

Change-Id: I5d8121d1734ec7f1991758360b829c7889540c71
diff --git a/tempest/services/compute/xml/servers_client.py b/tempest/services/compute/xml/servers_client.py
index 6d811a5..1ec4df0 100644
--- a/tempest/services/compute/xml/servers_client.py
+++ b/tempest/services/compute/xml/servers_client.py
@@ -111,9 +111,11 @@
 
 class ServersClientXML(RestClientXML):
 
-    def __init__(self, config, username, password, auth_url, tenant_name=None):
+    def __init__(self, config, username, password, auth_url, tenant_name=None,
+                 auth_version='v2'):
         super(ServersClientXML, self).__init__(config, username, password,
-                                               auth_url, tenant_name)
+                                               auth_url, tenant_name,
+                                               auth_version=auth_version)
         self.service = self.config.compute.catalog_type
 
     def _parse_key_value(self, node):