fixes #8318 - make errata indexing idempotent
Fixes #8322: display black icons if no errata needs to be applied.

Simply show black errata icons instead of calling attention to
them with green icons if no action needs to be performed.

http://projects.theforeman.org/issues/8322
Merge pull request #4807 from waldenraines/8322

Fixes #8322: display black icons if no errata needs to be applied.
Merge pull request #4806 from stbenjam/8318

fixes #8318 - make errata indexing idempotent
Fixes #7688: add a content hosts tab to the errata details.

Adds a content host tab to the errata details page that allows
the listing and syncing of applicable content hosts.

http://projects.theforeman.org/issues/7688