Stop using v2 identity API

v2 identity API was deprecated in Mitaka. There is only a one test
remaining that still relies on the v2 identity API. This patch replaces
v2 with v3.

Change-Id: Iaeb9153084c6864b0982902bbb2ae9c0233266a6
diff --git a/neutron/tests/tempest/api/base.py b/neutron/tests/tempest/api/base.py
index e735502..31285ac 100644
--- a/neutron/tests/tempest/api/base.py
+++ b/neutron/tests/tempest/api/base.py
@@ -430,8 +430,7 @@
     def setup_clients(cls):
         super(BaseAdminNetworkTest, cls).setup_clients()
         cls.admin_client = cls.os_admin.network_client
-        cls.identity_admin_client = cls.os_admin.tenants_client
-        cls.identity_admin_clientv3 = cls.os_admin.projects_client
+        cls.identity_admin_client = cls.os_admin.projects_client
 
     @classmethod
     def create_metering_label(cls, name, description):