Comment 5 for bug 1737214

Reviewed: https://review.openstack.org/539541
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=e521616afd14e6eedc0d3bfca0adf2179f4e05c2
Submitter: Zuul
Branch: stable/pike

commit e521616afd14e6eedc0d3bfca0adf2179f4e05c2
Author: Matt Riedemann <email address hidden>
Date: Fri Dec 8 13:15:50 2017 -0500

    Don't launch guestfs in a thread pool if guestfs.debug is enabled

    When guestfs.debug is enabled, we're handling callback events
    from guestfs and logging them at debug level. When guestfs
    is launched to inspect capabilities, that is currently done
    in an eventlet thread pool. Because of the concurrent logging
    along with the eventlet thread, we can hit an issue where eventlet
    tries to switch threads and fails and then we hang the launch
    call to guestfs, which hangs creating an instance.

    This change simply avoids using a thread pool to launch guestfs
    if guestfs.debug is True.

    Change-Id: I0ffe93a031154b123c8beff96a695df5a280b935
    Closes-Bug: #1737214
    (cherry picked from commit 7c30da13842469e641d171b6008a57d5db8c5d5e)