feat: Improve shutdown Delay default

[davinci26]

When a baseplate server is shutting down in k8s

• baseplate calls func (srv *Server) Shutdown(ctx context.Context) error which does the following:

• Shutdown works by first closing all open listeners

• k8s is attempting to remove the endpoint for the endpoints group and thus make (new) incoming traffic to the pod 0

This is a race condition because some callers are still trying to connect. We have empirically seen that the 5 second default is good enough for most services.

See also https://github.com/reddit/baseplate.go/pull/615