Drop these globals
Also include debian-archive-keyring

Thanks: Hans-Christoph Steiner
Closes: #748082
Update MIME type for .gpg
Revert "Drop these globals"

This reverts commit 2147bd800ad1cc3f8a2916f42d1d5810ec8b9341.
Cycle through possible apt keyrings

Thanks: Paul Wise
Closes: #747163