Instance disappeared during wait for destroy should be a warning not an error

[Phil Day]

Currently Nova logs an error if a libvirt domain disappears during while waiting for it to be destroyed, but the code actually treats this (correctly) as a recoverable situation since the end result is the required one. Hence this should be logged as a warning not an error.

This may help wit some of the gate failures: https://bugs.launchpad.net/nova/+bug/1300279

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/104192
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=2fee082e9267c75a1e676361d975e52ac9ad86f8
Submitter: Jenkins
Branch: master

commit 2fee082e9267c75a1e676361d975e52ac9ad86f8
Author: Phil Day <email address hidden>
Date: Wed Jul 2 13:22:13 2014 +0000

    Change instance disappeared during destroy from Error to Warning

    Currently Nova logs an error if a libvirt domain disappears during
    while waiting for it to be destroyed, but the code actually treats
    this (correctly) as a recoverable situation since the end result
    is the required one. Hence this should be logged as a warning not
    an error.

    Change-Id: Ie72cd11e22c5f049d3263e58bec286914798147a
    Closes-bug: #1336767