Another v3_onion_services variable failure

[rmol]

Description

The v3_onion_services Ansible variable being undefined strikes again, this time in the Tor onion services: upgrade to v2 QA test in the 1.0.0 test plan.

Steps to Reproduce

Run through the 1.0.0 test plan to get to Tor onion services: upgrade to v2 QA .

Expected Behavior

That the test plan could be completed.

Actual Behavior

An error is thrown at the Confirm that a valid set of SSH auth files is present task.

Comments

See also #4762.

This time, instead of playing whack-a-mole by adding the new variable to another Ansible defaults file, let's add a set_fact in the validate_tails_environment.yml playbook, so no matter how that playbook is used, v3_onion_services will be defined.