Run playbooks with only those roles defined thus far

So that a job lower in the inheritance hierarchy does not alter
the behavior of playbooks defined higher in the hierarchy, run
each playbook with only the roles that were present on the job
at the point in the inheritance hierarchy that playbook was
defined.

Change-Id: I06f4aff5340f48a09dae2cd95180531fa572b85e
7 files changed