Comment 3 for bug 1461182

My hypothesis is that ironic-conductor is seeing this issue because it is a server, but does also make outgoing calls and so it never creates a Client instance, and therefore the option isn't being registered. Since the option is needed by both the client and the server, it should be registered by both in oslo.messaging, so that's what the patch in comment #2 does. There's also a patch to ironic to instantiate a Client just to test the theory (https://review.openstack.org/#/c/187713), but we wouldn't want to land that patch.