This patch fixes bug 2616 and makes http_put more equivalent to http_post.
    
    url is of <type 'unicode>; body is of <type 'str'>
    Somewhere in the urllib2 package something happens like: url + body
    To do unicode + str, the str is implicetly converted to unicode.
    However bytes >128 cannot be represented in unicode and post-review crashes.
    eg: u'www.reviewboard.com' + "\x81" => error
    The solution:
    str(u'www.reviewboard.com') + "\x81" => 'www.reviewboard.com\x81'
    
    It seems the str(url) is already in place for the http_post function, but not for http_put.
    This patch makes unicode work and makes http_put more similar to http_post.