[3.6] bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None. (GH-4073).  (#4075)

* bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None. (#4073)

(cherry picked from commit daeefd2e)

* [3.6] bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None. (GH-4073).
(cherry picked from commit daeefd2e)