Fix admin tenant credential

Change-Id: Ie23fc998954a831312d21ca91a315e39c5fd34c2
diff --git a/tempest/clients.py b/tempest/clients.py
index fd46656..9c1a0f1 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -445,6 +445,6 @@
         base = super(OrchestrationManager, self)
         base.__init__(CONF.identity.admin_username,
                       CONF.identity.admin_password,
-                      CONF.identity.tenant_name,
+                      CONF.identity.admin_tenant_name,
                       interface=interface,
                       service=service)