netty defrerals and executor exception handling

[softprops]

We may be able to capture and handle at least one runtime exception throw when submitting a callable to the deferrable executor 1. This can potentially throw a RejectedExceptionException 2 if the server is shutting down. I think I may have captured this case the the following gist

https://gist.github.com/02267eac2f32970f9cf2

I think the server was shutting down in this case which caused the rejected exception 3 It may be safe to catch that and check if the executor is shutdown or terminated before re-throwing the exception