Add fallback to Class.newInstance.

  - In some scenarios, if a class doesn't have a constructor defined, Class.getConstructor() will fail, but Class.newInstance() won't fail. Not sure on the logic behind that one, Java.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1587455 13f79535-47bb-0310-9956-ffa450edef68