httpproxy: added missing fallback
httpproxy: added missing fallback

If no protocol (http, https) is given, then https:// will be used as default protocol.
cjellick/rancher,cjellick/rancher,rancherio/rancher,rancher/rancher,rancherio/rancher,rancher/rancher,cjellick/rancher,rancher/rancher,rancher/rancher