2.x: increase sleep time in XFlatMapTest

Author: akarnokd

src/test/java/io/reactivex/XFlatMapTest.java

@@ -30,7 +30,7 @@
 
 public class XFlatMapTest {
 
-    static final int SLEEP_AFTER_CANCEL = 200;
+    static final int SLEEP_AFTER_CANCEL = 500;
 
     final CyclicBarrier cb = new CyclicBarrier(2);