Disable spawner shutdown option

I've identified a problem when using the same launch file for the spawner python script and the controller_manager node. When using Ctrl-C to end the launch file, the controller_manager immediatley shutsdown but the spawner gets stuck because it is attempting to shutdown each controller it previously started, but the shutdown service is already ended with the controller_manager. 

I know for some hardware use cases, by passing the unload/shutdown service could be bad. But when using ros_control for baxter in the same launch file, this is a needed feature so that it doesn't unnecessarily hang.