Fix a crash on Python 3.9 if there are active greenlets during interpreter shutdown
https://greenlet.readthedocs.io/en/latest/changes.html#id4
Signed-off-by: Ankur Tyagi <ankur.tyagi85@gmail.com>
Signed-off-by: Anuj Mittal <anuj.mittal@oss.qualcomm.com>
