Adds a new abstract parent job for the following kayobe deploy jobs:
kayobe-overcloud-centos
kayobe-overcloud-upgrade-centos
kayobe-seed-centos
kayobe-seed-upgrade-centos
This parent includes commonly used variables, and pre-run and post-run
playbooks for preparing and executing diagnostics, plus other
initialisation.
Change-Id: I9ab89fbc49bb32d86af56d50ec3914740e65d0f8