Connection pool leak in spring-cloud-gateway-server-mvc when retrying with Apache HTTP client

[johan1a]

Describe the bug
I suspect that leased connections are not released back into the connection pool when an error is encountered, and the Apache HTTP client is used in combination with the retry filter. I think it is because the response body is not read before throwing a RetryException.

It seems that if something like the following is added to RetryFilterFunctions, right before this line of code, the connections get released back again:

        InputStream responseInputStream = MvcUtils.getAttribute(request, MvcUtils.CLIENT_RESPONSE_INPUT_STREAM_ATTR);
        StreamUtils.copy(responseInputStream, OutputStream.nullOutputStream());

Sample
Here is a repo that reproduces the issue: https://github.com/johan1a/spring-cloud-gateway-mvc-connection-test/tree/master