MongoDB daily dumps - possible corruption in 9 files

We were importing all daily .tar.gz archives from `http://ghtorrent-downloads.ewi.tudelft.nl/mongo-daily/`

The tar program failed due to an unexpected EOF in the following archives after two attempts to re-download:

- All from `mongo-dump-2016-01-02.tar.gz` to `mongo-dump-2016-01-08.tar.gz`
- `mongo-dump-2016-01-13.tar.gz`, and
- `mongo-dump-2018-07-31.tar.gz` (which is 0 bytes)
