Bugfix: Abort robustness

I found a set of corner cases that can only
be triggered when a ppg2 is 'abort'ed, i.e. partially
evaluated with regards to the ephemeral jobs.

The problem happend when an Ephemeral was invalidated,
done, it's output changed, and the downstreams were only
partially run.

It would go into a state where it would complain
that the ephemeral had changed it's output, and that it mustn't do so,
because in the new ppg2 run it was considered 'validated'.

This is now fixed.