[DOC] Document Kerberos in CDH not enabled

[Ken Chen]

Currently we have already added Sentry services into CDH plugin. However, we have not enabled Kerberos service in the cluster, so the Sentry service does really take effect, and users cannot really use Kerberos authentication in the cluster. We need to notify this in the document at this stage, before we can integrate the Kerberos service and reconfigure the whole cluster by it in the future.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/165289

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/165289
Committed: https://git.openstack.org/cgit/openstack/sahara/commit/?id=e0be2761b6e3bba08e177f18d44278272a1717fa
Submitter: Jenkins
Branch: master

commit e0be2761b6e3bba08e177f18d44278272a1717fa
Author: Ken Chen <email address hidden>
Date: Wed Mar 18 12:38:30 2015 +0800

    Notify Kerberos and Sentry do not take effect

    In the CDH plugin document, notify that Sentry service does not
    really take effect, for Kerberos authentication is not enabled in
    the cluster (need future implementation).

    Closes-Bug: #1433407
    Change-Id: I43665b394c81a2e3742ab2c31257f6ae7084b6be