Fix custom post status bug (#12706)

WordPress has some bugs associated with custom post statuses. It's been in trac for over 10 years.
https://core.trac.wordpress.org/ticket/12706

With CP's business focus, it can be a viable CMS for publishers. Publishers have different workflows for publishing articles/stories. EditFlow plugin introduced a feature to customize post statuses to give publishers a way to move posts through their workflows.

It would be a great differentiator for CP to fix annoying bugs that WP doesn't consider important.