[1.2.X] Fixed #15371 -- Ensure that a superuser created with the...

[1.2.X] 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.

Backport of r15631 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15632 bcc190cf-cafb-0310-a4f2-bffc1f526a37