Fixed #15371 -- Ensure that a superuser created with the createsuperuser...

Fixed #15371 -- Ensure that a superuser created with the createsuperuser management command with --noinput has an invalid password, not a blank password. Thanks to yishaibeeri for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15631 bcc190cf-cafb-0310-a4f2-bffc1f526a37