Split resource_setup for identity tests

Split up the resource_setup method for all the identity tests, as per the
latest spec.

Partially-implements bp:resource-cleanup

Change-Id: Ie3f90b708c3f16bcd29ac25eb8cba709faaf818f
diff --git a/tempest/api/identity/admin/v3/test_regions.py b/tempest/api/identity/admin/v3/test_regions.py
index 359c0cf..2ea7107 100644
--- a/tempest/api/identity/admin/v3/test_regions.py
+++ b/tempest/api/identity/admin/v3/test_regions.py
@@ -23,10 +23,14 @@
 class RegionsTestJSON(base.BaseIdentityV3AdminTest):
 
     @classmethod
+    def setup_clients(cls):
+        super(RegionsTestJSON, cls).setup_clients()
+        cls.client = cls.region_client
+
+    @classmethod
     def resource_setup(cls):
         super(RegionsTestJSON, cls).resource_setup()
         cls.setup_regions = list()
-        cls.client = cls.region_client
         for i in range(2):
             r_description = data_utils.rand_name('description-')
             region = cls.client.create_region(r_description)