[doc] Check for usage of same Cephx ID as manila service

[OpenStack Infra]

https://review.openstack.org/349718
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/manila" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit bd21193decf596ffcc5e285c114eba122986e7cb
Author: Dustin Schoenbrun <email address hidden>
Date: Mon Aug 1 17:24:21 2016 -0400

    Check for usage of same Cephx ID as manila service

    There is an issue that happens when access is granted to a manila share
    using the same Cephx ID that Manila uses when it is communicating with
    the Ceph backend (e.g. the identity specified by the cephfs_auth_id
    configuration option). When a request is made to revoke access to the
    share with that Cephx ID, the share will become stuck in the
    "deleting" state.

    This commit adds logic to the _allow_access method in the CephFS Native
    driver that checks to see if the Cephx ID given is the same that Manila
    is using for its communication with the Ceph backend. If that is the
    case, the creation of the access rule will fail with an error.

    APIImpact
    DocImpact

    Change-Id: Ida89b0061db1c8780a19475510b830d013a5c154
    Closes-Bug: #1608592

[Goutham Pacha Ravi (gouthamr)]

Dustin: Any documentation to be written in the devref/user guide for this change that you committed?

[Tom Barron (tpb)]

I am closing this one as not requiring documentation. The error message printed out if a manila service user's credentials are used for ordinary user share access allow operation is quite clear. Also, although this is something that might happen in a test environment, it would be unusual and an evidently dubious practice for a cloud administrator to set up a manila (or any other) service user and then use the credentials for the service user in a context of ordinary cloud user operations.