Use location header (redirect URL) for http codes between 300 and 400 (redirects).

Try to adjust its arguments in only if they are URLs  and point to proxy instance 
(i.e. it should point to remore instance).  


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@23573 20353a03-c40f-0410-a6d1-a30d3c3de9de