New product certificate for RHEL8

Summary

As a user of RHEL8, I want houndigrade to look for 479.pem so my images will be correctly identified.

Acceptance Criteria

• Verify images with 479.pem are correctly identified as RHEL.
  • be sure to update our minimal test images in https://gitlab.com/cloudigrade/houndigrade-test-data and the local testing process that uses them with docker-compose

Assumptions and Questions

• Based on what I found by looking at some RHEL8 AMIs, it seems that the new product certificate is 479.pem, but we are currently only looking for 69.pem.