no moving around of TempFiles anymore

It means GC will later delete a file with the tempfiles name. Which might be the next TempFiles file.

Here's what I observed:

* Test 1 would simulate a file upload.
* The uploaded file is stored in a TempFile
* The uploaded file is moved to another TempFile
* Test 1 proceeds and ends

* Test 2 simulates another file upload
* The uploaded file is stored in a TempFile with the same name as in
Test 1 because the Test 1 one has been moved.
* Garbage Collector runs and cleans up TempFiles from test 1
* file from test 2 is removed by TempFile#finalize from test 1 because
it has the same filename
* Test 2 can't find file and fails.