Don't duplicate final state payload #1309
Description
If the worker knows that it has already sent the final state for a run (because there's only one leaf node and it sent it on step:complete and there's only one path to that leaf node, etc., etc.) then it shouldn't DOUBLE the final state by sending that payload again.
In fact, right now we're doubling the final state sent over the wire in 99% of cases.
Rather, send final_dataclip_id if the dataclip has already been sent before. And watch out for timing issues. (What if run:complete arrives at lightning before step:complete? Is that possible?)