Use addClassResourceCleanup in test_list_projects

Replaces resource_cleanup with addClassResourceCleanup in
test_list_projects.

cls.projects was used only for resource_cleanup so that is
removed too. cls.project_ids is used in the tests.

Change-Id: Ia585d42b9d140b18e72871b7ce2ba833a64347af
diff --git a/tempest/api/identity/admin/v3/test_list_projects.py b/tempest/api/identity/admin/v3/test_list_projects.py
index 25dd52b..82664e8 100644
--- a/tempest/api/identity/admin/v3/test_list_projects.py
+++ b/tempest/api/identity/admin/v3/test_list_projects.py
@@ -27,32 +27,27 @@
         # Create a domain
         cls.domain = cls.create_domain()
         # Create project with domain
-        cls.projects = list()
         cls.p1_name = data_utils.rand_name('project')
         cls.p1 = cls.projects_client.create_project(
             cls.p1_name, enabled=False,
             domain_id=cls.domain['id'])['project']
-        cls.projects.append(cls.p1)
+        cls.addClassResourceCleanup(cls.projects_client.delete_project,
+                                    cls.p1['id'])
         cls.project_ids.append(cls.p1['id'])
         # Create default project
         p2_name = data_utils.rand_name('project')
         cls.p2 = cls.projects_client.create_project(p2_name)['project']
-        cls.projects.append(cls.p2)
+        cls.addClassResourceCleanup(cls.projects_client.delete_project,
+                                    cls.p2['id'])
         cls.project_ids.append(cls.p2['id'])
         # Create a new project (p3) using p2 as parent project
         p3_name = data_utils.rand_name('project')
         cls.p3 = cls.projects_client.create_project(
             p3_name, parent_id=cls.p2['id'])['project']
-        cls.projects.append(cls.p3)
+        cls.addClassResourceCleanup(cls.projects_client.delete_project,
+                                    cls.p3['id'])
         cls.project_ids.append(cls.p3['id'])
 
-    @classmethod
-    def resource_cleanup(cls):
-        # Cleanup the projects created during setup in inverse order
-        for project in reversed(cls.projects):
-            cls.projects_client.delete_project(project['id'])
-        super(ListProjectsTestJSON, cls).resource_cleanup()
-
     @decorators.idempotent_id('1d830662-22ad-427c-8c3e-4ec854b0af44')
     def test_list_projects(self):
         # List projects