The seed-fu gem wraps all seeds in a transaction:
https://github.com/mbleigh/seed-fu/blob/34c054c914858c3d7685f83d16dea5c0e2114561/lib/seed-fu/runner.rb#L35.
We can skip the Sidekiq transaction check for seeding test fixtures.

Closes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/351