Will take effect when Zuul is running this change:
I74702fd7d37358e6f4caa7e7ac0a3ede73184077
This change also adds that feature to the Zuul config and enables
it for OpenStack. It also adds the ability to specify HTML in a
commentlink (and uses it).
Change-Id: Idb4ad8e6079165d681271987a92cab5d8b7c81be