OperationContextImpl leaks to OperationContextImpl.OperationContextServiceRegistry

WorkerResourceDefinition.WorkerResource is holding a ref to the OperationContextImpl.OperationContextServiceRegistry. That's not a static class so that leaks the original OperationContextImpl.

Fix is to make it static and when the op is done disconnect the OC the way we do with OperationContextImpl.ContextServiceTarget.