mod_proxy_cluster returns 404 now instead of 503 when there's no matching context

With https://github.com/modcluster/mod_proxy_cluster/commit/2c459baf097940b65c94a898da3edc950d1c8402, JBCS httpd 2.4.57 now returns a 404 if there's no matching context even when a manual ProxyPass is used. That had always been a 503 instead with JBCS httpd 2.4.51 and earlier so this response code change can be undesired for some mod_cluster users.

This could be seen in a common scenario where all the app server instances are stopped so the context isn't currently present on the balancer. With 2.4.51 and before, the balancer responds with 503, which could be preferred as it suggests there is a technical issue with the application preventing its access temporarily so it can be retried while a 404 is suggesting more so that the content simply isn't present and so may be incorrectly requested content.

Could we revert this response code change or perhaps make it configurable if it'll give a 404 or a 503 in such a case?