Looper runp produces `default_project_record_identifier` folder with an empty stats.yaml

[donaldcampbelljr]

This is a workaround so that looper runp does not fail by not passing a record_identifier to pipestat during the initial pipestat instantiation when outputing results to different result files (stats.yaml).

Unfortunately, it is confusing users, so we should think of a better way to do this: https://github.com/databio/pepatac/issues/272