Comment 3 for bug 1000261

Reviewed: https://review.openstack.org/7518
Committed: http://github.com/openstack/nova/commit/2b3bbc49da7ea7eebbc046e746db1c085b08a425
Submitter: Jenkins
Branch: stable/essex

commit 2b3bbc49da7ea7eebbc046e746db1c085b08a425
Author: Pádraig Brady <email address hidden>
Date: Wed May 16 13:44:46 2012 +0100

    handle updated qemu-img info output

    Originally `qemu-img info` always output an (actual path: ...)
    even if it was duplicated with that already on the line.

     $ instances=/var/lib/nova/instances/
     $ qemu-img info $instances/instance-00000017/disk | grep 'backing'
     backing file: $instances/_base/24083... (actual path: $the_same)

    Whereas after the change referenced at:
    https://lists.gnu.org/archive/html/qemu-devel/2012-05/msg01468.html
    It suppresses a duplicate (actual path:)

     $ instances=/var/lib/nova/instances/
     $ qemu-img info $instances/instance-00000017/disk | grep 'backing'
     backing file: $instances/_base/24083...

    * nova/virt/libvirt/utils.py (get_disk_backing_file):
    Avoid an indexError exception when parsing the newer format.
    Fixes bug 1000261

    Change-Id: Ie2889b6da8a5c93e0e874e7a330529f6e6e71b0b
    (cherry picked from commit 0624b7aab0c0fe4869111ad8e302151548d6ba20)