xensm volume driver: backend_add broken

[Renuka Apte]

Tried to add a backend of type nfs. Volume driver crashes on add.
Reverting 77495cfe fixes it.

The logic for adding backends was written in a way that if the Storage repository (SR) needs to be created, it will not have a uuid associated with it. The uuid is provided by Xen when the SR is first created. This probably changed with 77495cfe.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/7288

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/7953

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/7953
Committed: http://github.com/openstack/nova/commit/9e337dac2960bbe8eaa4fbe3a8e5ca3e5e228936
Submitter: Jenkins
Branch: master

commit 9e337dac2960bbe8eaa4fbe3a8e5ca3e5e228936
Author: Renuka Apte <email address hidden>
Date: Tue May 29 11:45:57 2012 -0700

    Revert "Fix nova-manage backend_add with sr_uuid"

    Fixes bug 988596

    Change 77495cfe breaks storage manager, as it makes a
    wrong assumption about nova-manage. The sr-uuid must be
    generated and provided by the xenapi storage manager.

    When the volume service is started, SM volume driver will
    create a new SR for everything that does not have an
    existing sr_uuid and will populate the db with the result.
    It will only introduce the SRs that do have one. The introduce
    will work only if the uuid provided is something SM understands.

    This partially reverts commit 77495cfed17f12f225e11fbc10e0f8db516dadf2.
    Changes in db are left intact.

    Change-Id: I8405ac905a15f829f704951b94297f3b6f6c0a29