EnhancedQueueExecutor causes class loader leaks

EnhancedQueueExecutor does not managed its threads context class loaders. By default the TCCL that is assigned to a thread will be the TCCL at creation time, which can be a deployments TCCL.

This results in class loader leaks, as this deployments TCCL can then never be cleaned. In addition to this it means that the TCCL that tasks are run with is undefined, and can even be the TCCL of an unrelated deployment.