plugin/forward: add REFUSED test (#1878)

add a test to see if we copy the rcode correctly. Some minor cleanup in
import ordering and renaming NewUpstream to New as we already are in the
upstream package.

plugin/auto/setup.go

@@ -153,7 +153,7 @@ func autoParse(c *caddy.Controller) (Auto, error) {
 					return a, c.ArgErr()
 				}
 				var err error
-				a.loader.upstream, err = upstream.NewUpstream(args)
+				a.loader.upstream, err = upstream.New(args)
 				if err != nil {
 					return a, err
 				}