Ansible prepare step of imported plan does not work

[mkluson]

When you use import plan feature [1] and the imported plan has one of prepare steps implemented via Ansible, the execution fails, because it can not find the playbook. E.g.: ERROR! the playbook: /var/ARTIFACTS/git-masternbv9uido/ansible/setup_to_run_leapp.yml could not be found

[1] https://tmt.readthedocs.io/en/stable/spec/plans.html#import-plans