As initially most tests fail, they have allow_failures defined so that
testing anyway proceeds all the way to the final 'upgrade extras' stage.
All of these tests work for downstream Debian packaging of MariaDB 10.4
and should eventually pass on upstream MariaDB 10.5 as well.
Also upstream the Debian autopkgtests from MariaDB 10.4 in Debian so that
pipeline includes running mtr.
