[1.2.X] Fixed #13140 -- Ensure that request headers are preserved through...

[1.2.X] Fixed #13140 -- Ensure that request headers are preserved through redirect chains in the test client. Thanks to David Novakovic for the report.

Backport of r13620 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13621 bcc190cf-cafb-0310-a4f2-bffc1f526a37