Add a generic Walk()'er to list a bucket, optinally prefix (#9026)

This generic Walk() is used by likes of Lifecyle, or
KMS to rotate keys or any other functionality which
relies on this functionality.

cmd/object-handlers.go

@@ -1896,6 +1896,9 @@ func (api objectAPIHandlers) PutObjectPartHandler(w http.ResponseWriter, r *http
 		return
 	}
 
+	// To detect if the client has disconnected.
+	r.Body = &detectDisconnect{r.Body, r.Context().Done()}
+
 	// X-Amz-Copy-Source shouldn't be set for this call.
 	if _, ok := r.Header[xhttp.AmzCopySource]; ok {
 		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidCopySource), r.URL, guessIsBrowserReq(r))