Heat supports deferred operations via keystone trusts,
and we'd like to make that the default. To do this, we
require a new role, which is the default role specified
in heat.conf trusts_delegated_roles, heat_stack_owner.
Add the role to the admin/demo users so they can create
heat stacks when we make deferred_auth_method=trusts the
default.
Change-Id: Idfc70ee89428c23f5965e643486ff2ad9566471c
Related-Bug: #1286157