Comment 6 for bug 1814177

Reviewed: https://review.openstack.org/640595
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=40771bc155fe28977c805aed5f60b5d84b1ac2bc
Submitter: Zuul
Branch: stable/rocky

commit 40771bc155fe28977c805aed5f60b5d84b1ac2bc
Author: Matt Riedemann <email address hidden>
Date: Thu Jan 31 17:36:47 2019 -0500

    Fix race in test_volume_swap_server_with_error

    Change I03c8e8225e51fd80580772752c0b292987e34218 added
    another notification to the list checked in
    test_volume_swap_server_with_error and then change
    Id587967ea4f9980c292492e2f659bf55fb037b28 relied on
    checking the last notification in the list (compute.exception)
    but per the note in the test, that last exception can
    race to show up by the time we check the size of the
    notification list which can result in an IndexError.

    This change fixes the race by just waiting for the
    compute.exception notification rather than the racy
    _wait_until_swap_volume_error which depended on the
    cinder fixture swap_error variable (which is removed
    in this change).

    Change-Id: I8165fcd98e11b9155640559a36ae90a38f63c0dd
    Closes-Bug: #1814177
    (cherry picked from commit 03e4e3ce1357123f9f53a3901a17a64f160653a4)