tests: Fix race issue in application-update test
When retrieving the entry from the database, it can be still at the previous version and not updated yet.
As a consequence, the test would fail with a wrong download_url (the previous one).
To fix that, the entry is retrieved multiple times until it has the correct updated version. If the version is not up-to-date after 10 tries, the test will fail.
The race condition can also make the test fail when checking the different states (The download could be over when checking). Those are not checked anymore.