We have identified that keystone does not support pagination properly
like other services do. Use oslo_db.sqlalchemy helper to paginate
projects (and implicitly domains) list requests.
Introduce `max_db_limit` configuration option to allow operator to limit
maximum amount of entries to be fetched from the database (takes
precedence over user requested page size or dedicated default resource
limit).
Change-Id: I6d19a8d8827b7fb5c4b88f5b3b9dd899c5f3db5f
37b02476e7