Avoid busy retry (dpkp#192)

Test test/test_consumer_group.py::test_group and
test/test_admin_integration.py::test_describe_consumer_group_exists
busy-retry and this might have caused Java not having enough CPU time on
GitHub runner, and result in test failure.

Author: orange-kao

test/test_admin_integration.py

@@ -220,6 +220,7 @@ def consumer_thread(i, group_id):
                 else:
                     sleep(1)
             assert time() < timeout, "timeout waiting for assignments"
+            sleep(0.25)
 
         info('Group stabilized; verifying assignment')
         output = kafka_admin_client.describe_consumer_groups(group_id_list)

test/test_consumer_group.py

@@ -111,6 +111,7 @@ def consumer_thread(i):
                     logging.info('Rejoining: %s, generations: %s', rejoining, generations)
                     time.sleep(1)
             assert time.time() < timeout, "timeout waiting for assignments"
+            time.sleep(0.25)
 
         logging.info('Group stabilized; verifying assignment')
         group_assignment = set()