Queens: what's left for rolling upgrades

[Ruby Loo]

This isn't really a bug, just tracking what is left to do wrt rolling upgrades, so we don't forget.

- enable the TODO's in the code and documentation, for checking the object versions to make sure they are compatible, before allowing an 'ironic-dbsync upgrade' or 'ironic-dbsync online_data_migrations' to be done.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/497703

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/497703
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=6a91b38ca48eea2892a5a82b4369f1f9b277d019
Submitter: Zuul
Branch: master

commit 6a91b38ca48eea2892a5a82b4369f1f9b277d019
Author: Ruby Loo <email address hidden>
Date: Thu Aug 24 20:56:22 2017 -0400

    ironic-dbsync: check object versions

    Now that we have rolling upgrades and the version column was
    added and populated in the Pike release, we can add checks to
    make sure the versions of objects in the DB are compatible
    with this ironic release, before ironic-dbsync's upgrade or
    online_data_migrations does its work. These ironic-dbsync
    calls are made as part of upgrading to this (Queens) release.

    Change-Id: I68758f8a29d483f5c0a7439fa2ea2962b2eb4124
    Partial-Bug: #1708243

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/516374

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/516374
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=64ebfb35ed2931ac10762bd2ceb085b8c93e7595
Submitter: Zuul
Branch: master

commit 64ebfb35ed2931ac10762bd2ceb085b8c93e7595
Author: Ruby Loo <email address hidden>
Date: Mon Oct 30 12:10:56 2017 -0400

    [reno] Update ironic-dbsync's check object version

    This updates the release note pertaining to ironic-dbsync's
    check of the object versions, to be explicit that these are the
    database records that correspond to the IronicObjects.

    This is a follow up to 6a91b38ca48eea2892a5a82b4369f1f9b277d019.

    Change-Id: I1e2b3dc60529551746a0c7a258e5ce3cf509f59f
    Partial-Bug: #1708243