Fix intermittent testing failure with eventstream
Previously it was possible that the erring future would not have run
rendering the count in this test incorrect
@@ -25,6 +25,7 @@ def test_eventstream(c, s, *workers):
futures = c.map(div, [1] * 10, range(10))
total = c.submit(sum, futures[1:])
yield _wait(total)
+ yield _wait(futures)
assert len(es.buffer) == 11
