Use a ring channel to avoid blocking write of events (#2082)

* Use a ring channel to avoid blocking write of events

* Add eapache/channels dependency

vendor/github.com/eapache/channels/black_hole_test.go

@@ -0,0 +1,26 @@
+package channels
+
+import "testing"
+
+func TestBlackHole(t *testing.T) {
+	discard := NewBlackHole()
+
+	for i := 0; i < 1000; i++ {
+		discard.In() <- i
+	}
+
+	discard.Close()
+
+	if discard.Len() != 1000 {
+		t.Error("blackhole expected 1000 was", discard.Len())
+	}
+
+	// no asserts here, this is just for the race detector's benefit
+	ch := NewBlackHole()
+	go ch.Len()
+	go ch.Cap()
+
+	go func() {
+		ch.In() <- nil
+	}()
+}