Issue #22922: Fix ProactorEventLoop.close()

Call _stop_accept_futures() before sestting the _closed attribute, otherwise
call_soon() raises an error.
Issue #22922: Fix ProactorEventLoop.close()

Call _stop_accept_futures() before sestting the _closed attribute, otherwise
call_soon() raises an error.
Closes #22429, asyncio: Fix EventLoop.run_until_complete(), don't stop the
event loop if a BaseException is raised, because the event loop is already
stopped.
Merge 3.4 (asyncio)