This is the only user of fetch_actor_and_object which previously just
always preteneded to be successful. For all the activity types handled
here, we absolutely need the referenced object to be able to process it
(other than Announce whether or not processing those activity types for
unknown remote objects is desirable in the first place is up for debate)
All other users of the similar fetch_actor already properly check success.
Note, this currently lumps all reolv failure reasons together,
so even e.g. boosts of MRF rejected posts will still exhaust all
retries. The following commit improves on this.
0cd4040db6