Remove untyped volume/snapshot online-data-migrations

[Brian Rosmaita]

Online data migrations were added in Train; they should have been removed in Ussuri, but were not. However, there was a bug in the Train online migration that needs to be fixed in Ussuri and backported to Train (see Bug #1893107), so the migrations should NOT be removed from Ussuri.

No need to include a check in the upgrade status tool because the volume_type_id column was made non-nullable in Ussuri, and hence there can't be any untyped volumes/snapshots to worry about (whether deleted or not.)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/748300

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/748300
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=7268ec61005d89f2ee75408daea47e14421a03a0
Submitter: Zuul
Branch: master

commit 7268ec61005d89f2ee75408daea47e14421a03a0
Author: Brian Rosmaita <email address hidden>
Date: Wed Aug 26 16:18:46 2020 -0400

    Remove Train online data migrations

    Online data migrations are supposed to be removed in the following
    development cycle, so these migrations from Train are overdue.

    This change should NOT be backported to Ussuri, however, as there
    was a bug in the Train migrations and a fixed version of the migrations
    may still need to be run in Ussuri. See Bug #1893107 for more info.

    Change-Id: I78681ea89762790f544178725999903a41d75ad1
    Closes-bug: #1893114