Improve upgrades CI coverage with standalone installer

The main goal of this work is to improve coverage of service upgrade_tasks in tripleo ci upgrades jobs, by making use of the Standalone_installer_work. Using a standalone node as a single node ‘overcloud’ allows us to exercise both controlplane and dataplane services in the same job and within current resources of 2 nodes and 3 hours. Furthermore and once proven successful this approach can be extended to include even single service upgrades testing to vastly improve on the current coverage with respect to all the service upgrade_tasks defined in the tripleo-heat-templates (which is currently minimal).