Separate projects client from identity V3 client

Partially implements blueprint consistent-service-method-names

Change-Id: I236b2468de81539ae06937c2644c9840bea68b96
diff --git a/tempest/api/identity/admin/v3/test_credentials.py b/tempest/api/identity/admin/v3/test_credentials.py
index b81bff7..0e76d37 100644
--- a/tempest/api/identity/admin/v3/test_credentials.py
+++ b/tempest/api/identity/admin/v3/test_credentials.py
@@ -31,7 +31,7 @@
         u_email = '%s@testmail.tm' % u_name
         u_password = data_utils.rand_password()
         for i in range(2):
-            cls.project = cls.client.create_project(
+            cls.project = cls.projects_client.create_project(
                 data_utils.rand_name('project'),
                 description=data_utils.rand_name('project-desc'))['project']
             cls.projects.append(cls.project['id'])
@@ -44,7 +44,7 @@
     def resource_cleanup(cls):
         cls.client.delete_user(cls.user_body['id'])
         for p in cls.projects:
-            cls.client.delete_project(p)
+            cls.projects_client.delete_project(p)
         super(CredentialsTestJSON, cls).resource_cleanup()
 
     def _delete_credential(self, cred_id):