Rework test_workflow_group()

Drop assertion "cwtask.eid in results" which is already implicitly checked by "results[cwtask.eid]"
Only run a group(success(), success()), which is enough for the scope of this
test and make it compatible with celery 4 where nested groups are rewrited in a
single group.
Wait and test results of all subtasks, not only the first one.

test/test_celerytask.py

@@ -176,17 +176,14 @@ class CeleryTaskTC(BaseCeleryTaskTC):
             cwtask = start_async_task(cnx, task)
             cnx.commit()
             self.assertEqual(cwtask.task_name, u'celery.group')
-
             results = run_all_tasks(cnx)
-            self.assertIn(cwtask.eid, results)
             self.assertEqual(results[cwtask.eid].get(), [5, 9])
-
-            children = cwtask.reverse_parent_task
-            self.assertEqual(len(children), 2)
-            self.assertEqual(children[0].task_name, u'add')
-            task_id = children[0].cw_adapt_to('ICeleryTask').task_id
-            result = self.wait_async_task(cnx, task_id)
-            self.assertEqual(result.get(), 5)
+            subtasks = cwtask.reverse_parent_task
+            self.assertEqual(len(subtasks), 2)
+            for subtask, expected in zip(subtasks, [5, 9]):
+                self.wait_async_task(cnx, subtask.task_id)
+                result = subtask.cw_adapt_to('ICeleryTask').result.get()
+                self.assertEqual(result, expected)
 
     def test_workflow_chord(self):
         with self.admin_access.repo_cnx() as cnx:
@@ -252,14 +249,10 @@ class CeleryTaskTC(BaseCeleryTaskTC):
             def success():
                 return celery.signature("success")
 
-            graph = celery.group(
-                celery.group(success(), success()),
-                celery.group(success(), success()),
-                success())
-            task = start_async_task(cnx, graph)
+            task = start_async_task(cnx, celery.group(success(), success()))
             cnx.commit()
             task_ids = set([t.task_id for t in task.child_tasks()])
-            self.assertEqual(len(task_ids), 8)
+            self.assertEqual(len(task_ids), 3)
             with mock.patch('celery.app.control.Control.revoke') as revoke:
                 task.cw_adapt_to('ICeleryTask').revoke()
             self.assertEqual(revoke.call_count, 1)