cmd/relui: fix website upload username

Unlike the coordinator, the website doesn't want the user- prefix on the
username.

For golang/go#51797.

Change-Id: I169bdf1dd8ffd7cad6fccb2cf752be4271efe094
Reviewed-on: https://go-review.googlesource.com/c/build/+/411063
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Heschi Kreinick <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Run-TryBot: Heschi Kreinick <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: heschi

cmd/relui/main.go

@@ -19,6 +19,7 @@ import (
 	"math/rand"
 	"net/http"
 	"net/url"
+	"strings"
 	"time"
 
 	"cloud.google.com/go/storage"
@@ -182,7 +183,7 @@ func publishFile(uploadURL string, auth buildlet.UserPass, f *relui.WebsiteFile)
 	if err != nil {
 		return fmt.Errorf("invalid website upload URL %q: %v", *websiteUploadURL, err)
 	}
-	u.Query().Set("user", auth.Username)
+	u.Query().Set("user", strings.TrimPrefix("user-", auth.Username))
 	u.Query().Set("key", auth.Password)
 	resp, err := http.Post(u.String(), "application/json", bytes.NewReader(req))
 	if err != nil {