test_epoll.test_control_and_wait flakes from improper poll() usage

[kevinGC]

Bug report

test_epoll.test_control_and_wait can flake. In the test we wait for events on two file descriptors. This is done in a single call to select.epoll's poll() function. However, it is valid for the OS to return only one event via poll() and the next via a subsequent call to poll(). This rarely happens, but it can cause the test to fail despite properly functioning polling.

Your environment

• CPython versions tested on: 3.10.2
• Operating system and architecture: Linux 5.19.11 and gVisor

Linked PRs

• gh-102795: Fix use of poll in test_epoll's test_control_and_wait #102796
• [3.11] gh-102795: Fix use of poll in test_epoll's test_control_and_wait (GH-102796) #104173