http2/h2i: send RequestURI as path, to not lose query args

Change-Id: I95161246bbb1a29490c0058593ee36bcb706e1d9
Reviewed-on: https://go-review.googlesource.com/34820
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

http2/h2i/h2i.go

@@ -473,7 +473,7 @@ func (app *h2i) encodeHeaders(req *http.Request) []byte {
 		host = req.URL.Host
 	}
 
-	path := req.URL.Path
+	path := req.RequestURI
 	if path == "" {
 		path = "/"
 	}