Major Description
Currently, task.checkpoint.factory is either in the config or it's not. If it's in the config, we call Class.forName() on the value to get the checkpoint factory. It'd be nice if we ignored the value if the factory is set to an empty string. Currently, if you set:
task.checkpoint.factory=
We will call Class.forName("") in the container, which will fail. We should treat an empty value the same as a null, and skip the checkpoint manager setup.