[3.5] bpo-29406: asyncio SSL contexts leak sockets after calling close with certain...

[3.5] bpo-29406: asyncio SSL contexts leak sockets after calling close with certain servers (GH-409) (#2063)

* bpo-29406: asyncio SSL contexts leak sockets after calling close with certain servers (#409)

(cherry picked from commit a608d2d5a7f1aabe9bcbfc220135c5e126189390)

* [3.5] bpo-29406: asyncio SSL contexts leak sockets after calling close with certain servers (GH-409)

* asyncio SSL contexts leak sockets after calling close with certain servers

* cleanup _shutdown_timeout_handle on _fatal_error.
(cherry picked from commit a608d2d5a7f1aabe9bcbfc220135c5e126189390)