Wait for Foreman tasks in backup integration tests #894

The backup integration fixture exercises successful archive creation immediately after deployment. Satellite and IOP deployments can still have valid Foreman tasks in progress, but the fixture invokes foremanctl backup without --wait-for-tasks. The production preflight then correctly rejects the backup before any archive is written.

This is reproducible in the exact-head CI for PR #892:

• Satellite non-air-gapped job
• IOP Stream 10 job
• IOP Stream 9 job

The success-path fixture should opt into waiting for active tasks. The user-facing default must remain fail-fast unless --wait-for-tasks is explicitly requested.