[1.2.X] Fixed #14612 - Password reset page leaks valid user ids publicly.

Thanks to PaulM for the report.

Backport of [14456] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14458 bcc190cf-cafb-0310-a4f2-bffc1f526a37