Bugfix attachments (fixes #474)

[Maksimymis]

Context

Cloning bugfix (attachments are cloned in the step and in the test) (fixes #474)

Checklist

• [x] Sign Allure CLA
• [x] Provide unit tests

[rodolfoholy]

This one too

[delatrie]

Not relevant since Pytest-BDD v4.1 when target_fixture for then and when was introduced