Comment 2 for bug 1621493

Chatting with d0ugal on #tripleo, returning a Mistral Result with the 'error' attribute set is the expected pattern, as Mistral will mark a Task as failed whenever this attribute is set. The issue comes from the client side: in the future we probably want to move these methods to be entirely done via workflows (e.g. using following the JSON approach at https://review.openstack.org/#/c/347830/ though that'll likely needs to be done in other places too). In the meantime we need to check each call's result.