Pulp

As mentioned in #7773 , we should refactor our logic to add repos to the system (in a robust & configurable manner) into another role like pulp_repos.

I propose the following design:

1. This is a dependency role. pulp_common, pulp_redis, pulp_database, will all depend on it.
2. When a role like pulp_common depends on it, it passes variables like __pulp_repos_epel: true to denote which repos the role needs. It passes variables via roles/pulp_common/meta/main.yml : dependencies:
3. If a user wants to disable the logic to add the repo (if they added it manually), they'll pass a variable like pulp_repos_epel: false to disable it.
4. Existing variables for configuring how we add the repos to the system, like epel_release_packages, should still used.

This logic is found in:

• roles/pulp_common/tasks/ambiguously-named-repo.yml
• roles/pulp_common/tasks/repos.yml