Comment 10 for bug 1781286

Reviewed: https://review.openstack.org/582412
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=276130c6d1637f8e0f39ba274e2619a115a8fa1a
Submitter: Zuul
Branch: master

commit 276130c6d1637f8e0f39ba274e2619a115a8fa1a
Author: Matt Riedemann <email address hidden>
Date: Thu Jul 12 18:25:07 2018 -0400

    Add note about reschedules and num_attempts in filter_properties

    The "retry" entry in filter_properties is not set if reschedules
    are disabled, which happens in these cases:

    1. [scheduler]/max_attempts=1
    2. The server is forced to a specific host and/or node.

    More times than I'd like to admit, I've had to re-learn that
    filter_properties['retry']['num_attempts'] will always be >1 in
    conductor build_instances during a reschedule because if
    reschedules are disabled, the compute service aborts the build
    on failure and we don't even get back to conductor.

    This change adds a note since it's hard to keep in your head how
    the retry logic is all tied together from the API, superconductor,
    compute and cell conductor during a reschedule scenario.

    Change-Id: I83536b179000f41f9618a4b6f2a16b4440fd61ba
    Related-Bug: #1781286