1131260 - Add verify_ssl to repo_auth.conf.

The new implementation of certificate validation is inefficient. This
commit adds a new verify_ssl setting to repo_auth.conf for users who
wish to use Apache to verify client certificates when using repository
protection.

https://bugzilla.redhat.com/show_bug.cgi?id=1131260
Add the 2.4.0 label back to the release notes.
Fail fast when repo CA bundles aren't provided.
Fix a docs typo.