Hmm, c.f. [this view](https://github.com/crowbar/barclamp-crowbar/blob/release/pebbles/master/crowbar_framework/app/views/nodes/actions.html.haml#L10) - it seems that unknown node state is handled inconsistently.  Sometimes it is set to `'unknown'` when `nil`; other times the `titlecase` method is directly called on it, which implicitly assumes that it cannot be `nil`.

The underlying question is whether this value is intended to be consumed programmatically, or exposed via any UI.  If the former, then it should remain untranslated, and a value of `nil` should be acceptable.  If the latter, then it should be translated, and a value of `nil` should not be acceptable.  Unfortunately however it seems that currently the answer is "both", which is bad design and which is currently causing bugs like this `avoid undefined method 'foo' for nil:NilClass` error which I'm attempting to fix in this PR.  @cloudedge - any thoughts on which is more correct?