Gate governance with project-config
Gate governance with project-config

To avoid the potential to typo new project names in governance, we're
adding a linter to the governance repo to ensure the project exists in
project-config[1]. Add project-config as a required project for the
governance linters job so that new projects need not wait for the
project-config patch to merge before the governance patch can pass
tests.

[1] https://review.openstack.org/583637

Change-Id: I8be9eae083ad2b1e9387704e064d104b196a0d1b

openstack-infra/project-config,openstack-infra/project-config