[test][prefix] Make all databases root folder point to a valid location

This will allow the docker tests to more easily setup and
cleanup its content.

While the folder is not used as these databases are generative
only, docker will create it anyway as mounting a non-exisiting
folder will trigger its creation with the daemon ownership
7 jobs for standardize_test_database_root_folder in 4 minutes and 59 seconds (queued for 8 seconds)