SHIRNKWRAP-102 provided configuration for a Domain to be associated with an ExecutorService (to be supplied, for instance, by a runtime environment or host container). Honor this configuration in the ZIP Exporter, if defined. If no explicit ES has been set, let the current implementation default to a new, local-stack-only ES be used per each call. If the ES is defined in the configuration, use it, but do not shut it down (this is now the responsibility of the caller, as they've created/supplied the ES).