Currently outstanding_global_views values are only decremented during
the end of epoch cleanup, but not when handle_end_of_result_collection
is called for the specific uid that actually triggered the result
collection (which is specifically NOT a cleanup event).
This changes outstanding_global_views values to be a set of outstanding
uids, instead of a count. This allows handle_end_of_result_collection
to remove any uids from the set as it sees them.
f80f2f2a08