If the response is set and we can't change the status through
ServerHttpResponse any more, allow the error signal to propagate and
let the individual server adapters handle it. Ultimately that should
result in closing the connection.
On Servlet containers, we check one last time if the response is
committed (we may not have filled the buffer). If not then save
the exception as a request attribute, dispatch, and re-throw it on the
container thread.
On Undertow access the connection and close it.
On Netty just let the error through to Reactor Netty.
Issue: SPR-16051
f05175586e