Adding roles to deploy the overcloud with instack

This commit adds the roles and playbook entries to
prepare and deploy the overcloud. Roles to test the
overcloud will be in a separate commit.
It also adds common defaults and tasks for the stack
user as this will be duplicated in deploying the
overcloud and testing it.

Change-Id: I3c612fe72f186af5ea2b241c22664ef14b1fb216