Jostle logic seems to randomly stop working

[Dmitri Kourennyi]

Adding a little bit more information:

When the issue cropped up again, I tried running
"unbound-control dump_requestlist" to inspect the list, expecting it to 
be full
of requests that are stuck for some reason. Instead I found that it was
completely empty. Yet incoming queries were constantly being rejected.

Then I tried "unbound-control flush_requestlist" to see if it had any 
effect,
and sure enough, it resolves the issue, even though there doesn't appear 
to be
anything to flush.

When I get a spare moment, I'll try to add some more logging in that 
part of the
code, see if I can specifically determine what condition is failing that 
is
causing the queries to be dropped.