`async/map` output channel not close, when has some input channel not closed, even if I closed one channel of inputs.

```clojure
(def c1 (chan))
(def c2 (chan))
(def out (a/map vector [c1 c2]))
(a/close! c1)
(a/<!! out) ;; will hangs until I put item to `c2` or close `c2`
```

I think the better way is close output channel immediately when any of input channels closed.