#9351: set_defaults on subparser is no longer ignored if set on parent.

Before, if a default was set on the parent parser, any default for that
variable set via set_defaults on a subparser would be ignored.  Now
the subparser set_defaults is honored.

Patch by Jyrki Pullianinen.
#18853: Fix resource warning in shlex's __main__ section.

Report and original fix by Vajrasky Kok.