Some tests are flaky

For example:

```
2024-10-13T10:07:26.1267332Z EFUploadServiceTest > testOneFileRedundantMultiPart() FAILED
2024-10-13T10:07:26.1268735Z     java.lang.IndexOutOfBoundsException at EFUploadServiceTest.kt:678
```

This is inevitably a race condition. The task hasn't finished by the time the test checks the result.