Comment 2 for bug 1057719

Reviewed: https://review.openstack.org/13788
Committed: http://github.com/openstack/nova/commit/628a993ce29cfdee00463c16b932f23e30bc52bf
Submitter: Jenkins
Branch: master

commit 628a993ce29cfdee00463c16b932f23e30bc52bf
Author: Vishvananda Ishaya <email address hidden>
Date: Thu Sep 27 12:32:32 2012 -0700

    libvirt: Improve the idempotency of iscsi detach

    When detaching an iscsi volume it is possible for the iscsi commands
    to run concurrently, causing a target to be deleted by one greenthread
    while the other is continuing. When removing the iscsi connection,
    we should always ignore exit code 21 because that means that the
    target has already been removed.

    Fixes bug 1057719

    Change-Id: I0c9f2623f85a817e2be506f9a6d523d45c76848a