Fix socket and pipe leaks in :mod:`asyncio` when ``protocol_factory()`` raises
in :meth:`loop.create_datagram_endpoint
<asyncio.loop.create_datagram_endpoint>`, :meth:`loop.connect_read_pipe
<asyncio.loop.connect_read_pipe>`, and :meth:`loop.connect_write_pipe
<asyncio.loop.connect_write_pipe>`. The socket or pipe is now closed instead
of leaking until garbage collection.
