Fix handling of fallback to optparse.OptionParser
Fix handling of fallback to optparse.OptionParser

By the time the code here runs, it's too late to be modifying
base.BaseCommand.option_list; in fact doing so causes an OptionConflictError if
you later call another management command "recursively" while you're running
the first one.

We want to leave BaseCommand's option_list untouched (it's `()` by default in
Django 1.8+) in case the command we are wrapping has already upgraded to
argparse. BUT, if it hasn't, we'll get an OptionParser back, and can tack our
argument on at the last minute.

incuna/django-configurations