When rebaking and in various other places for posts, we
run through the uploads and call `update_secure_status` on
each of them.
However, if the secure status didn't change, we were still
calling S3 to change the ACL, which would have been a noop
in many cases and takes ~1 second per call, slowing things
down a lot.
Also, we didn't account for the s3_acls_enabled site setting
being false here, and in the specs doing an assertion
that `Discourse.store.update_ACL` is not called doesn't
work; `Discourse.store` isn't a singleton, it re-initializes
`FileStore::S3Store.new` every single time.