http2/h2demo: allow alternate hostnames for http and https links
http2/h2demo: allow alternate hostnames for http and https links

Fixes golang/go#12905

Change-Id: I73b3041f06ca93ad0e75251ca32f077fa9eafe8d
Reviewed-on: https://go-review.googlesource.com/15826
Reviewed-by: Arnout Engelen <0a5e220122bc195b848436603de35259556d873f@bzzt.net>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

cmars/tools,cesanta/goxnet,DramaFever/golang.org-x-net,cmars/tools,cmars/tools,golang/net,albertjin/golang-net,cmars/tools,albertjin/golang-net,DramaFever/golang.org-x-net,cesanta/goxnet