Works now similar to how https://github.com/zendframework/zend-eventmanager/blob/master/src/EventManagerAwareTrait.php works.

Such that attached listeners set in constructor will not be overwritten
later by Zend/Mvc's initializer.

This way the listeners in ZF2 style do not have to be adapted.

The only way to use them was via the shared service manager. But in ZF3
this manager is only instantiated after construction. Thus this has no
function anymore.