[S-RBAC] Integration with Designate should use service and user token

[Slawek Kaplonski]

This was originally comment made by gmann in https://bugs.launchpad.net/neutron/+bug/2078518:

For service-to-service interaction, neutron should pass both token user token + service token to create the record set. Designate need to use the service token for authentication and an user token (admin token) for record set creation. This is how we need to do for service role implementation.

Along with designate side, we need changes in neutron also.