Because of a limitation in GnuPG we need to have the Jessie archive
signing key in the list of VerifyRelease key IDs for the Debian
reprepro mirror. Also some suites (currently buster-backports) are
signed by a subkey of an archive signing key, so add the "+" suffix
to all these key IDs indicating subkey signatures are also allowed.
As always, Debian signing keys are published and available here:
https://ftp-master.debian.org/keys.html
Change-Id: Iedce38318718a18ace7b2c638755a7d7d4dcd69b
5a096f3705