update entry Attributes.Mtime = time.Now().Unix()

fix https://github.com/seaweedfs/seaweedfs/issues/4337

weed/s3api/s3api_object_copy_handlers.go

@@ -46,6 +46,7 @@ func (s3a *S3ApiServer) CopyObjectHandler(w http.ResponseWriter, r *http.Request
 			return
 		}
 		entry.Extended, err = processMetadataBytes(r.Header, entry.Extended, replaceMeta, replaceTagging)
+		entry.Attributes.Mtime = time.Now().Unix()
 		if err != nil {
 			glog.Errorf("CopyObjectHandler ValidateTags error %s: %v", r.URL, err)
 			s3err.WriteErrorResponse(w, r, s3err.ErrInvalidTag)