Revert upstream commit 094d239e0261263de3799bb6bd1cc33f06833d8b "make test less
timing dependent", as it seems to intermittently create the following
regression:

  lein test :only clojure.core.async-test/ops-tests

  FAIL in (ops-tests) (async_test.clj:304)
  mult
  expected: (= nil (a/poll! t-1))
    actual: (not (= nil 2))

  lein test :only clojure.core.async-test/ops-tests

  FAIL in (ops-tests) (async_test.clj:305)
  mult
  expected: (= 1 (<!! t-2))
    actual: (not (= 1 2))

  lein test :only clojure.core.async-test/ops-tests

  FAIL in (ops-tests) (async_test.clj:306)
  mult
  expected: (= 2 (<!! t-1))
    actual: (not (= 2 3))
Index: core-async-clojure/src/test/clojure/clojure/core/async_test.clj
===================================================================
--- core-async-clojure.orig/src/test/clojure/clojure/core/async_test.clj
+++ core-async-clojure/src/test/clojure/clojure/core/async_test.clj
@@ -300,10 +300,10 @@
       (tap m t-2)
       (tap m t-3)
       (close! t-3)
-      (is (= 1 (<!! t-1)))
+      (is (= 1 (a/poll! t-1)))
       (is (= nil (a/poll! t-1))) ;; t-2 hasn't taken yet
-      (is (= 1 (<!! t-2)))
-      (is (= 2 (<!! t-1))) ;; now available
+      (is (= 1 (a/poll! t-2)))
+      (is (= 2 (a/poll! t-1))) ;; now available
       (is (= nil (a/poll! t-1)))))
 
   (testing "mix"