Description of problem:
When upgrading Satellite 6.8 to 6.9, there is a step to clean up old tasks (Procedures::ForemanTasks::Delete) which bails out with "failed to allocate memory" when it tries to backup 400.000 tasks.

Version-Release number of selected component (if applicable):
foreman_maintain 0.8.30, but should apply to all versions

How reproducible:
100%

Steps to Reproduce:
1. have a system with 400k tasks
2. try to make f-m backup/delete them

Actual results:
error

Expected results:
backup and delete works

Additional info:
I think the issue is that it tries to load ALL tasks into memory first, and then write them to disk. See export_csv in definitions/features/foreman_tasks.rb.