Before this change rclone would fail with
Failed to set modification time: InvalidObjectState: Operation is not valid for the source object's storage class
when attempting to set the modification time of an object in GLACIER.
After this change rclone will re-upload the object as part of a sync if it needs to change the modification time.
See: https://forum.rclone.org/t/suspected-bug-in-s3-or-compatible-sync-logic-to-glacier/10187