Description of problem:
This is tracker for the documentation changes required for Sahara since Kilo. 

The changes should be limited; apart from the packstack support already requested in rhbz#1232872, the following should be documented:

== Changed service type

'11.2.2. Create the OpenStack Data Processing Service Identity Records', and specifically 'Procedure 11.2. Configuring the OpenStack Data Processing service to authenticate through the Identity Service' refers to data_processing as the service type that needs to be created:


4. Create the sahara system item:
# keystone service-create --name=sahara --type=data_processing --description="OpenStack Data Processing"


This is now expected to be data-processing by clients (and tempest) by default, so it should be

4. Create the sahara system item:
# keystone service-create --name=sahara --type=data-processing --description="OpenStack Data Processing"


== Preferred packages/daemons

While the previous configuration with a unique daemon to be executed (openstack-sahara-all from openstack-sahara package) is still supported, the preferred way is the usage of openstack-sahara-api and openstack-sahara-engine daemons, shipped in the packages with the same names.

Affected documentation:

- 11.1. Install the OpenStack Data Processing Service Packages
Instead of openstack-sahara, the packages are openstack-sahara-api and openstack-sahara-engine.
 ⁠
- 11.3. Configure and Launch the OpenStack Data Processing Service
Refer to openstack-sahara-api and openstack-sahara-engine instead of openstack-sahara-all

I don't think that the the old way should be totally removed, but maybe it should be mentioned someone; for example, right now packstack installations use openstack-sahara and openstack-sahara-all (see https://bugzilla.redhat.com/show_bug.cgi?id=1232872#c0).