debian: Add md5 sum fallback when sha* checksum is missing in metadata
In order to check successful download of a package file, the debian loader will compare sha256 or sha1 checksum of the file with the one located in debian dsc file.
However for old debian-based distributions (some ubuntu old releases for instance) the only available checksum in the dsc file is a md5 sum.
So add a fallback to use md5 sum to check successful download when sha* checksum is missing in the dsc file.
Related to swh/infra/sysadm-environment#2400 (closed)
Migrated from D6750 (view on Phabricator)