Loader: Atomic write of files

[bschmalhofer]

A bit unrelated is a potential problem with writing files in the Loader. The writing of the loader files is not atomic. This means that another another process might detect the existence of the file, and the client might request it before it is completely written. In practice the timing is likely such that problems never occurs.

Originally posted by @bschmalhofer in #1325 (comment)

[bschmalhofer]

I still think that there is a potential problem with incomplete files being delivered by the web server. But simply switching to atomic writes might lead to concurrent writes to the same file, which might have bad effects too. So, let's not change the current behaviour as there are no current error reports.

Nevertheless some mild code improvements were applied. Closing the issue as wontfix,