Description of problem:
The openscap report files are not removed from the disk when the clean up command is executed.

Version-Release number of selected component (if applicable): 6.12, 6.11, 6.10

How reproducible:
Always

Steps to Reproduce:
1. Run 'foreman-rake reports:expire days=7 report_type=ForemanOpenscap::ArfReport'

Actual results:
the reports are removed from web UI and DB, but the files remain in /var/lib/foreman-proxy/openscap/reports/arf

Expected results:
The corresponding reports in /var/lib/foreman-proxy/openscap/reports/arf should get removed

Additional info:
Tested with Sat v6.12, v6.11 (RHEL8), and v6.10 (RHEL7) and exhibits the same behaviors.