Open Stack

Hi,

With https://review.openstack.org/492697 we are moving gating of Zuul
itself and some related job repos from Zuul v2 to Zuul v3.  As part of
this, we need to disable some of the checks that we perform on the
layout file.  That change disables the following checks for the
openstack-infra/* repos only:

* usage of the merge-check template
* at least one check job
* at least one gate job
* every gerrit project appears in zuul

The first three should only be needed for a short time while we continue
to construct the post and release pipelines in Zuul v3.  After that is
complete, we should be able to reinstate those checks, but we will need
to keep the final check disabled (for openstack-infra repos at least)
until Zuul v2 is retired.

-Jim