VyOS builds and HTTPS: build works again, HTTP still needs testing

We have restored VyOS builds. Nightly build should work as expected today, and you can build it by hand as well if you want. This is not exactly the end of the story for us since we need to finish some reconfiguration of Jenkins to accomodate the new setup, but nothing dramatic should happen to the ISO builds any soon, or so we hope.

HTTPS, however, is another story. It still doesn't work for me, and I'm not sure if it's APT itself to blame or anything in our build setup. Since this is not a pressing issue, I'm not going to put much effort into it right now, but if you have a build setup, please check if it works for you. If it doesn't work for anyone, then we can write it off as an APT issue.