The arguments to this call are still a little off.  I am looking at org.jgroups.stack.Configurator line 414 for an example of how JGroups does class loading.  Here is some code based on the main code base:
```java
Class<?> credsProviderClazz = null;
try {
  credsProviderClazz = Util.loadClass(credentials_provider_class, getClass());
}
catch( ClassNotFoundException e ) {
  throw new Exception("unable to load credentials provider class " + credentials_provider_class);
}
```