`IsOverridden` is only eventually consistent
`IsOverridden` is only eventually consistent

This is because up until now, the 'overridden' flags have been purely
an optimization to speed up future iterations over setups but correct-
ness of operation was guaranteed even without it. Since updating these
flags means some computational overhead, that update does not happen
in a "hot" code path, and therefore does not happen at the earliest
possible time.

Now that `IsOverridden` is exposed, eventual consistency is no longer
good enough, as this failing test demonstrates.

Moq/moq4