ActionFinish called after Action completion

The worker now calls ActionFinish on state to call home with the results of an Action.

The unit will not be set to an error state unless the API call to ActionFinish fails.  Any other errors generated by the Action will be encapsulated in the results message, which is sent back to state with the final state of the Action (complete or fail.)
can we rearrange the bit above to create the context and finalize it immediately on validation fail? Carrying this error through here is still a bit confusing -- and I don't think we lose anything by skipping straight over the state-writing.