Code cleanup for eventlet_utils.wait_fo_any

- waiter class renamed;
- unused member removed from it.

Change-Id: Id2510211ba726d8ebe17d8a63f6a95ecb761f46e
Update requirements from opentack/requirements

- sync requirements with global openstack requirements;
- fix flake8 errors.

Change-Id: I7430367726708787fc068e18506fbbb117d23952