This might help address #3015
This only affects rate timeouts. Normal fixed timeouts might deserve the same treatment, but that would require some additional locking to ensure we don't modify the sentinel value.
Prior to this, only the response body counted toward the HTTP/2 response data rate. This PR aligns the HTTP/2 logic closer to the HTTP/1.x logic and measures the rate for all HTTP/2 response data.
This PR also accounts for all response bytes written, not just those that immediately induced backpressure.
Stephen Halter