ActionFinish called after Action completion

The worker now calls ActionComplete or ActionFailed on state, depending
on the success state of the Action and any errors.

The hook is set to an error state if the Action hook is missing, or if
other errors take place during hook execution.  If the Action hook sets
a fail state, the Hook will not error, rather the Action will fail.

DEPENDS: https://github.com/juju/juju/pull/651
I do recall that as well -- didn't realize I hadn't addressed it, cognitive error.  My change must have gotten lost in a stale branch.

I did realize, however, that the only time hi.Kind is "ActionRequested", the immediate next step is to enforce that it's an Action (not a Hook with that name) by querying the Action's call parameters from State.  There are then multiple fail conditions which will be met if it's not one.