A record submitted after aclose(), from the loop or a thread, rebound the
dispatcher: a new queue and task that wrote to the sinks just closed. Now
aclose() closes it for good. Later records are dropped and counted under
"dispatcher closed" (new drop_reasons), with one warning; it never binds a
loop or starts a task again, and aclose() twice is a no-op. Calls made
after close are not kept in recent for linking.
flush() also waits for a record put just after queue.join() woke, which a
single join missed: a record a thread handed over just before aclose()
is delivered if it lands during the flush, else dropped and counted.
rsp2k
b28482fffc