Fix mapPipelinedJob

[RahimovIR]

mapPipelinedJob hangs when processing all incoming jobs is faster than closing <- true

also fixed the test

[Szer]

So, as I understand there is race condition.

Let's say there is one-element stream which we pipelining to synchronous Job which returns immediately.

It means that this code will start closing the stream

Job.tryIn 
        (xs |> iterJob (Ch.give inCh))
        (fun () -> closing <- true; Job.unit() )
       ...

And also loop() will start to listen to it's Alt.choose cases.
In case closing hasn't been settled to true YET, our loop will stuck on such cases

outCh // won't be satisfied, as all workers are done already
inCh // won't be satisfied, as stream has iterated
Alt.never() // has been picked because `if closing && usage = 0` returned false

So yes, adding closeCh instead of boolean flag, will help with that.

[Szer]

shouldn't it be IVar for closing?

[RahimovIR]

I will fix it, but a little later