- [bug] Extra logic has been added to the "flush"

- [bug] Extra logic has been added to the "flush"
    that occurs within Session.commit(), such that the
    extra state added by an after_flush() or
    after_flush_postexec() hook is also flushed in a
    subsequent flush, before the "commit" completes.
    Subsequent calls to flush() will continue until
    the after_flush hooks stop adding new state.
    An "overflow" counter of 100 is also in place,
    in the event of a broken after_flush() hook
    adding new content each time. [ticket:2566]