DistributedTaskPart get(timeout, TimeUnit) throws ClassCastException in case the execution is not finished after specified time

The issue appears almost every time the test is executed.

The case is the following:
1. Callable<Integer> is submitted to DistributedExecutorService for execution;
The callable body consists of simple Thread.sleep(time) which makes the callable to sleep for specific period of time.

2. Result is taken with get(long timeout, TimeUnit unit) method;
The timeout is given so that, it is much more shorter than the sleeping time of the callable. But sometimes it happens, that the get(timeout, unit) waits till the end. I guess this happens due to priority of threads.

3. In case of expected execution flow, i.e. if the method execution takes longer than the specified timeout, the following exception is thrown:

java.lang.ClassCastException: java.lang.Integer cannot be cast to java.util.Map
at org.infinispan.distexec.DefaultExecutorService$DistributedTaskPart.retrieveResult(DefaultExecutorService.java:882)
at org.infinispan.distexec.DefaultExecutorService$DistributedTaskPart.get(DefaultExecutorService.java:818)
at org.infinispan.distexec.DistributedExecutorTest.testSleepingCallableWithTimeoutOption(DistributedExecutorTest.java:336)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:74)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:673)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:846)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1170)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
at org.testng.TestRunner.runWorkers(TestRunner.java:1147)
at org.testng.TestRunner.privateRun(TestRunner.java:749)
at org.testng.TestRunner.run(TestRunner.java:600)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:317)
at org.testng.SuiteRunner.access$000(SuiteRunner.java:34)
at org.testng.SuiteRunner$SuiteWorker.run(SuiteRunner.java:351)
at org.testng.internal.thread.ThreadUtil$CountDownLatchedRunnable.run(ThreadUtil.java:147)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)

The pull request which contains tests reproducing/verifying the issue, is: https://github.com/infinispan/infinispan/pull/1425