Support CopyObject to same location for rclone

[wthorp]

https://forum.storj.io/t/s3-sync-does-not-work/16220?u=alexey
the AWS CLI didn't preserve the modification time with Gateway-MT. It preserves in their objects though.
The interesting thing that rclone sync with s3 protocol preserves the modification time and trying to update it if this is the only a difference (it will fail, because Failed to set modification time: NotImplemented: A header you provided implies functionality that is not implemented, so you need to use --no-update-modtime).

I think the the Last-Modified (actually created at) timestamp, like the rest of the metadata, is established at the time of object creation and immutable, thereafter. Therefore what rclone is doing is technically a call to CopyObject. We'd been waiting on MetaInfo for this, but I'll create a ticket for the upcoming sprint to see if we can fix this particular edge case entirely in the Gateways.

[storjBuildBot]

Change https://review.dev.storj.io/c/storj/gateway/+/6431 mentions this issue.