The recent Debian update broke some guest setup. Roll back.
CC: Julien Grall <julien@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Ian Jackson <iwj@xenproject.org>
TftpDiVersion_stretch 2020-09-24
TftpDiVersion_buster 2021-02-08
+DebianMirror_buster_armhf http://snapshot.debian.org/archive/debian/20210201T024125Z/
+
DebianSnapshotBackports_jessie http://snapshot.debian.org/archive/debian/20190206T211314Z/
# For ISO installs