[dav] 401 instead of 501 for deactivated webdav

pkg/dav/dav.go

@@ -30,7 +30,7 @@ const ANNEXPEEKSIZE = 1024
 
 func Dav(c *gctx.Context, handler *webdav.Handler) {
 	if !setting.WebDav.On {
-		c.WriteHeader(http.StatusNotImplemented)
+		c.WriteHeader(http.StatusUnauthorized)
 		return
 	}
 	if checkPerms(c) != nil {