[AS7-6546] Check the class name when adding a names handler that might already exist

Check the class name when adding a names handler that might already exist. This happens at the switch between the boot logging configuration and subsystem logging configuration. Subsystem logging always overrides boot logging.

An example is when a user changes the ```periodic-rotating-file-handler``` in the ```standalone.xml``` to a ```file-handler```.

The XML configuration will always override the ```logging.properties``` configuration.