Use hkp:// and port 80 for key retrieval on restricted networks

At both...

• Home, on a Spectrum cable internet connection in the Dallas area
• At work, in a heavily firewalled / proxied university network

... it is not possible to retrieve keys from --keyserver keyserver.ubuntu.com as this is using port 11371 on which outbound connections fail.

Most keyservers, including keyserver.ubuntu.com listen on the hkp hkps protocol at port 80 443 for this reason. I think it would be good to use --keyserver hkps://keyserver.ubuntu.com:443 by default to avoid issues on restrictive networks.

If this is not accepted I'll just need to manually modify when I am working on the package helpers.