http2/h2demo: update bug link, add idle conn timeouts
http2/h2demo: update bug link, add idle conn timeouts

Updates golang/go#14204

Change-Id: Id2598c77e2677a50988c00adc8751a9b87751202
Reviewed-on: https://go-review.googlesource.com/19159
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

cmars/tools,cesanta/goxnet,cesanta/goxnet,golang/net,cmars/tools,albertjin/golang-net,cmars/tools,cmars/tools,albertjin/golang-net