Add support for clients/endpoint_type parameter.
Note: Default to False now, because TripleO already sets this resource.
and we don't want duplicated resource.
Once we switch TripleO to use this new option, the default will
become os_service_default.
Change-Id: If707c5623c0e34e9219eeafdafaf0ac42daf5c8d
Closes-Bug: #1675409