Get the train of a component from the RC instead of deriving from the version

ref https://github.com/deis/workflow-manager/pull/59#discussion_r64781415

Start with the discussion linked from the issue and trace how the workflow manager currently derives a component's train from its version and reads the Kubernetes RC. Confirm the expected train source in that discussion; done means the component train comes from the RC rather than version derivation, with the relevant existing checks still passing.

Written by the indexing model from the issue text.