6736316: Timeout value in java/util/concurrent/locks/Lock/FlakyMutex.java is insufficient

Reviewed-by: chegar, dholmes, alanb

jdk/test/java/util/concurrent/locks/Lock/FlakyMutex.java

@@ -86,7 +86,7 @@ public class FlakyMutex implements Lock {
                 } catch (Throwable t) { unexpected(t); }}});}
         barrier.await();
         es.shutdown();
-        check(es.awaitTermination(10, TimeUnit.SECONDS));
+        check(es.awaitTermination(30, TimeUnit.SECONDS));
     }
 
     private static class FlakySync extends AbstractQueuedLongSynchronizer {