This will gracefully shut down the service instead of resulting in errors like
this:
```
Jan 24 10:11:11 foo livebook[981676]: 10:11:11.922 [error] GenServer :disksup terminating
Jan 24 10:11:11 foo livebook[981676]: ** (stop) {:port_died, :normal}
Jan 24 10:11:11 foo livebook[981676]: Last message: {:EXIT, #Port<0.8>, :normal}
Jan 24 10:11:11 foo livebook[981676]: 10:11:11.922 [error] GenServer :memsup terminating
Jan 24 10:11:11 foo livebook[981676]: ** (stop) {:port_died, :normal}
```
1ee8e72834