[netty#2744] Fix flakey HashedWheelTimerTest.testExecutionOnTime()

Motivation:

The calculation of the max wait time for HashedWheelTimerTest.testExecutionOnTime() was wrong and so the test sometimes failed.

Modifications:

Fix the max wait time.

Result:

No more test-failures

common/src/test/java/io/netty/util/HashedWheelTimerTest.java

@@ -131,7 +131,7 @@ public void run(final Timeout timeout) throws Exception {
     public void testExecutionOnTime() throws InterruptedException {
         int tickDuration = 200;
         int timeout = 125;
-        int maxTimeout = tickDuration + timeout + tickDuration;
+        int maxTimeout = 2 * (tickDuration + timeout);
         final HashedWheelTimer timer = new HashedWheelTimer(tickDuration, TimeUnit.MILLISECONDS);
         final BlockingQueue<Long> queue = new LinkedBlockingQueue<Long>();