Some objects (directories, origins, releases, revisions) will not be added into the storage
if they are provided as generator parameters to the Storage::*_add methods instead of lists.
This is why the swh-vault tests are currently failing as since the removal of the retry
mechanism in swh-loader-core, generators are provided as parameters to the Storage::*_add
methods while previously lists of objects were provided.
As a simple fix, ensure to transform generators into lists before processing the objects.