Appending URLs in case of redirect is incorrect

If the header returns an absolute path as a redirect, don't simply append the path to the old URL, remove the old absolute path first.

For example, original URL:

http://www.theregister.co.uk/2013/07/28/birmingham_uni_car_cracker_muzzled_by_lords/print.html

Redirect from header:

/Print/2013/07/28/birmingham_uni_car_cracker_muzzled_by_lords/

Incorrect result:

http://www.theregister.co.uk/2013/07/28/birmingham_uni_car_cracker_muzzled_by_lords/print.html/Print/2013/07/28/birmingham_uni_car_cracker_muzzled_by_lords/

Correct result after this patch:

http://www.theregister.co.uk/Print/2013/07/28/birmingham_uni_car_cracker_muzzled_by_lords/