Comment 4 for bug 1766306

Reviewed: https://review.openstack.org/563728
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=048fa2310014e6282e183da0abee87c73b6d71b9
Submitter: Zuul
Branch: master

commit 048fa2310014e6282e183da0abee87c73b6d71b9
Author: Matt Riedemann <email address hidden>
Date: Mon Apr 23 14:01:36 2018 -0400

    api-ref: mark block_device_mapping_v2.boot_index as required

    This was marked optional in change If57aa3e37 but it has
    only been optional since Queens due to change I8a3e7e6c4,
    before that you will get a 400 error if you do not provide
    boot_index in the BDMs, e.g.:

    2018-04-23 12:34:13,308 INFO [nova.api.openstack.wsgi] \
       HTTP exception thrown: Block Device Mapping is Invalid: \
       Boot sequence for the instance and image/block device \
       mapping combination is not valid.
    2018-04-23 12:34:13,310 INFO [nova.api.openstack.requestlog] \
       127.0.0.1 "POST /v2.1/6f70656e737461636b20342065766572/servers"
       status: 400 len: 164 microversion: 2.1 time: 0.129485

    One could argue that I8a3e7e6c4b72eb1c3707d54049d18dc29f606fe5
    is a behavior change that should have gone with a microversion,
    which if people agree with that, could be reverted separately.

    Change-Id: I14d44dbc0b6a8fb25932c333e695cad9edaefbed
    Closes-Bug: #1766306