Before this change, changing the case of a file on a case insensitive remote
would fatally panic when `--dry-run` was set, due to `moveOrCopyFile`
attempting to access the non-existent `tmpObj` it (would normally have)
created. After this change, the panic is avoided by skipping this step during
a `--dry-run` (with the usual "skipped as --dry-run is set" log message.)