bpo-37015: Ensure tasks created by _accept_connection2 due to AsyncMock are completed (GH-13661)

From 3.8 async functions used with mock.patch return an `AsyncMock`. `_accept_connection2` is an async function where create_task is also mocked. Don't mock `create_task` so that tasks are created out of coroutine returned by `AsyncMock` and the tasks are completed.


https://bugs.python.org/issue37015