[1.2.X] Fixed #14830 -- Ensure that radio buttons on inlines preserve their...

[1.2.X] Fixed #14830 -- Ensure that radio buttons on inlines preserve their default value. Thanks to Julien Phalip for the report and patch, and to antoinemartin for the diagnosis.

Backport of r15420 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15421 bcc190cf-cafb-0310-a4f2-bffc1f526a37