Use new syntax for base jobs
Change updated the syntax
for base jobs so that they must be defined with 'parent: null'.
Update our base jobs to reflect that.  Also, remove the explicit
parenting of the tarball job on base and rely on implicit parenting.
Depends-On:
- job:
name: base
+ parent: null
description: |
The base job for OpenStack's installation of Zuul.
- job:
name: base-test
+ parent: null
description: |
A job to test changes to the base job without disturbing the
main job in production. Not for general use.
- job:
name: publish-openstack-tarball
- parent: base
description: |
Publish job to upload artifacts to tarballs.openstack.org
post-run: playbooks/publish/openstack-tarball
