[3.7] bpo-33789: Backport test_asyncio fixes from master (GH-7478)

[3.7] bpo-33789: Backport test_asyncio fixes from master (GH-7478)

* bpo-33789: test_asyncio: Fix ResourceWarning (GH-7460)

* Close sockets and streams to fix ResourceWarning warnings
* Catch also OSError to hide a traceback on an expected handshake
  error

(cherry picked from commit 0eba7c39132614a5730cda6b340e18dfb2d30d14)

* bpo-33789, test_asyncio: Hide PendingDeprecationWarning (GH-7461)

Hide PendingDeprecationWarning in test__register_task_3().

(cherry picked from commit 7ed61e9431ee2c191aeeeb26f86a71bb90ab99fd)

* bpo-32676, test_asyncio: Fix warning in test_error_in_call_soon() (GH-7462)

Fix "<CoroWrapper ...> was never yielded from" warning in
PyTask_PyFuture_Tests.test_error_in_call_soon() of
test_asyncio.test_tasks.

Close manually the coroutine on error.

(cherry picked from commit 9f04f0df6fdb27190690bda949d213893d14e807)