CI: Database interfaces return empty sample list

Sometimes one of the CI jobs fails because a database returned an empty list when retrieving samples.

Has Mainly been seen on the macos-arm jobs, but always on one of both jobs (3.9,macos-arm or 3.10,macos-arm).

Re-running the failed job fixes the issue.

It could be an issue with having two jobs running on the same machine. If both share the same data directory: if the first job finishes and cleans the database definition file, the second one has no file to read and returns an empty sample list.