Adds nova unit-test job

Includes:
- roles/openstack/unit-tests/prep : prepares VM: upgrade and reboot
- roles/openstack/unit-tests/setup: sets up the testbed for test-run
- roles/openstack/unit-tests/run  : runs test and prints result

Change-Id: I0975a269e5d24af5e819986b877c9d769748fb7b
retries twice

Change-Id: I8f343a84ef6f002057acfc627fd322b7195f9405