[BUG] Game download can get stuck in a loop if validation is unsuccessul

[Pacodastre]

Describe the bug
Drop can get stuck in a validation/downloading loop if games files have been modified since they were imported.

To Reproduce
Steps to reproduce the behavior:

1. Import a game version into drop
2. Modify a file within the game folder
3. In the drop-app client, download the game at the version you imported
4. The client app will first download the game, then verify its file.
5. The drop app will see that a file doesn't pass the verification step and re-download the file.
6. The drop app will then get stuck in a loop verifying the files, seeing that one file has the wrong checksum, re-download it, and re-verify the files, and so on.

Expected behavior
Drop tries a maximum of 3 times to download and verify game files. If re-downloading the files doesn't fix it, drop should break the loop and return an error to the client.