New config parsing breaks plugins

[Paul Bourke]

Since moving to the oslo.config method of parsing kolla-build.conf, the plugin functionality no longer works.

e.g. the following is not picked up:

[neutron-server-plugin-networking-arista]
type = git
location = https://github.com/openstack/networking-arista
reference = stable/kilo

This seems to be because oslo.config requires config options to be registered prior to parsing, so the dynamic sections aren't present in conf._groups. The above section is seen in conf.list_all_sections, but so far I can't find a call to access this as a group.

Can someone with more oslo.config knowledge pitch in if this is possible, otherwise we need to come up with a new strategy for supporting plugins.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/268211

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/268211
Committed: https://git.openstack.org/cgit/openstack/kolla/commit/?id=477fc18bd0febb2d53c0c5053ccff76ae1589d25
Submitter: Jenkins
Branch: master

commit 477fc18bd0febb2d53c0c5053ccff76ae1589d25
Author: Paul Bourke <email address hidden>
Date: Fri Jan 15 15:48:28 2016 +0000

    Fix image plugin functionality for oslo.config

    The new oslo.config style parsing for kolla-build.conf stopped plugins
    from working. This patch fixes it and adds a unit test.

    Co-Authored-By: Jeffrey Zhang <email address hidden>
    Closes-Bug: 1534556
    Change-Id: I135797c733ae0cae040a009c364073769b19e4eb