Fix excessive retries missing --max-duration timeout - fixes #4504

This change checks the context whenever rclone might retry, and
doesn't retry if the current context has an error.

This fixes the pathological behaviour of `--max-duration` refusing to
exit because all the context deadline exceeded errors were being
retried.

This unfortunately meant changing the shouldRetry logic in every
backend and doing a lot of context propagation.

See: https://forum.rclone.org/t/add-flag-to-exit-immediately-when-max-duration-reached/22723

backend/fichier/object.go

@@ -94,7 +94,7 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (io.ReadClo
 
 	err = o.fs.pacer.Call(func() (bool, error) {
 		resp, err = o.fs.rest.Call(ctx, &opts)
-		return shouldRetry(resp, err)
+		return shouldRetry(ctx, resp, err)
 	})
 
 	if err != nil {