=con #15600 Fix config in PeekMailboxSpec

Test now passes with expected output : 
```
Hello
World
World
[ERROR] [07/30/2014 10:16:53.161] [MySystem-akka.actor.default-dispatcher-3] [akka://MySystem/user/myActor] DONTWANNA
java.lang.Exception: DONTWANNA
	at akka.contrib.mailbox.MyActor.doStuff(PeekMailboxSpec.scala:106)
	at akka.contrib.mailbox.MyActor$$anonfun$receive$2.applyOrElse(PeekMailboxSpec.scala:99)
	at akka.actor.Actor$class.aroundReceive(Actor.scala:465)
	at akka.contrib.mailbox.MyActor.aroundReceive(PeekMailboxSpec.scala:95)
	at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
	at akka.actor.ActorCell.invoke(ActorCell.scala:487)
	at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:241)
	at akka.dispatch.Mailbox.run(Mailbox.scala:223)
	at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:393)
	at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
	at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
	at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
	at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
```