[examples testing] restore code
For some reason https://github.com/huggingface/transformers/pull/5512 re-added temp dir creation code that was removed by
https://github.com/huggingface/transformers/pull/6494 in the process undoing what the latter PR did those tests, leading to the temp dir created twice in a row.

I see now that it was an older PR that was committed much later, so that explains why the new code was not noticed.

@Joel-hanson
Sorry, @stas00 I didn't notice that.<|||||>All is good, it was easy to miss, @Joel-hanson. 