Fix HTTP 301 redirect, set the Host explicitly

Fix 301 redirect to use the Host of the redirect location. See discussion on the forum: http://forum.soapui.org/viewtopic.php?t=23090

Another, earlier Pull request (https://github.com/SmartBear/soapui/pull/42) was closed, because I didn't sign the contributor agreement yet. I did that just now so it should all be in place.