Strip protocol from remote authority

In Google cloud shell the host header is 127.0.0.1:8080 instead of the
actual URL. This is what we write out to the HTML so VS Code can pick it
up. However cloud shell rewrites this string when found in the HTML
before serving it so it becomes https://8080-[...].appspot.com,
resulting in an extra unexpected https:// in the
URI (vscode-remote://https://8080[...]). The resulting malformed URI
causes the extension host to exit.

- Fixes #1471
- Fixes #1468
- Fixes #1440 (most likely).