Description of problem:
* Some 3rd party (NFV) require the admin user to have the admin role in the Default domain.

* Some deployers automatically add the admin user to the Default domain post deployment but it could probably be better to have keystone-manage bootstrap a domain with --bootstrap-domain-name.

* We already assign user to project and create the Default domain in the bootstrapping procedure.

Version-Release number of selected component (if applicable):
Any

How reproducible:
All the time

Steps to Reproduce:
1. Deploy overcloud
2. Verify role for admin user in Default domain

Actual results:
Admin user doesn't have admin role in Default domain

Expected results:
Admin user should have admin role in Default domain

Additional info:
At least Trillio is known to require this.

Adam Young says the right place to do it would be in the upstream keystone-manager bootstrap.