handle req['host'] in update_uri.
* lib/net/http/generic_request.rb
(Net::HTTP::GenericRequest#update_uri):
use req['host'] if it is explicitly set. Even if URI is given,
it is already used for the initial value of req['host'].
Therefore overwritten value should be respected. [Bug #10054]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47077 b2dd03c8-39d4-4d8f-98ff-823fe69b080e