profiler: fix race in TestProfilerPassthrough (DataDog#601)

The test previously was trying to read from the p.out channel, which was racing against the send() function and uploadFunc

This patch makes the test read from the correct out channel and eliminates an unnecessary loop.

profiler/profiler_test.go

@@ -202,14 +202,12 @@ func TestProfilerPassthrough(t *testing.T) {
 	}
 	p.run()
 	var bat batch
-loop:
-	for {
-		select {
-		case bat = <-p.out:
-			break loop
-		case <-time.After(500 * time.Millisecond):
-			t.Fatal("time expired")
-		}
+	select {
+	case bat = <-out:
+	// TODO (knusbaum) this timeout is long because we were seeing timeouts at 500ms.
+	// it would be nice to have a time-independent way to test this
+	case <-time.After(1000 * time.Millisecond):
+		t.Fatal("time expired")
 	}
 
 	assert.Equal(t, 2, len(bat.profiles))