Delete a temporary file, when a distributor finishes downloading it, but it ends up having an unexpected size

[daniil-berg]

Currently we throw an UnexpectedFileSize error, if the number of bytes loaded does not exactly match the size that the distributor was "promised", when its /api/distributor/copy/... endpoint was called. The file is then not considered "controlled" by that node, but it remains present on disk at its temporary path.

There is no cleanup task like there is with the storage file controller and since the file is not considered controlled by the node, the periodic DistributionController.free_up_dist_nodes task does not clean it up either. I have not tested this, but I think in such a case the temporary file would remain there indefinitely. In the worst case, the disk could end up littered with "data corpses".