Comment 5 for bug 1729439

Reviewed: https://review.openstack.org/526802
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=0d005ffcb69b8c5be3228957f7dfb8809b811742
Submitter: Zuul
Branch: stable/pike

commit 0d005ffcb69b8c5be3228957f7dfb8809b811742
Author: Zane Bitter <email address hidden>
Date: Wed Nov 1 18:03:20 2017 -0400

    Fix non-destructive upgrade for deprecated res types in convergence

    When a user updates from a deprecated resource type to an
    equivalent-but-differently-named one (e.g. from
    OS::Heat::SoftwareDeployments to OS::Heat::SoftwareDeploymentGroup), Heat
    is supposed to change the type without replacing the resource as it would
    normally do when a resource type changes. This was broken in convergence,
    because since 45073226752c58d640ea5a59b7e532c022a4939b the new Resource
    object we create during the check_resource operation (using the new type's
    plugin) is no longer automatically initialised with data from the database
    as resources in the legacy path are.

    Move the substitution checking to the Resource.load() method, so that it
    now returns an instance of the new plugin where allowed. In the actual
    update_convergence() method then we need only check that the resource class
    is the one we'd expect from the new template, and replace the resource if
    not.

    We do have a test that is designed to check that this is working, but in it
    we didn't compare the physical IDs of the resource that is potentially
    getting replaced, but rather the physical IDs of some other resource that
    can't possibly get modified (surprise! it doesn't change).

    Conflicts:
     heat/engine/resource.py

    This patch is modified with respect to the one on master, since the
    branch does not contain 960f626c2455b77e654aea1d79597fadb91dc894. Thus,
    resource_owning_stack.defn is substituted for initial_stk_defn and
    curr_stack.defn for latest_stk_defn.

    Change-Id: I75778abc303525a71d0a918f7192f00a43c21284
    Closes-Bug: #1729439
    (cherry picked from commit 93b4551d9a1ff9194b30a079f02db691129c69b0)