ParentClassLoaderFinder default strategy is broken for embedded OpenEJB

ParentClassLoaderFinder default strategy always uses the ClassLoader which got used to load OpenEJB.class. But this algorithm is broken for all scenarios where a classloader hierarchy is in place.

Instead of this we should use the Thread.currentThread.getContextClassLoader() by default.

Please note that is is effectively not possible to set a custom ParrentClassLoaderFinder (via SystemInstance.get().setComponent(ParentClassLoaderFinder.class,... ) when using EJBContainer.createEJBContainer() as this gets cleared via SystemInstance.reset() at boot time.