Limit scope of test suite to avoid unnecessary test failures

Limit tests to main suite and skip replication tests. This helps avoid
obscure test failures that are most likely build environment specific
things and not real failures. Having as a requirement to have all those
new and obscure tests pass everywhere is unreasonable in the stable
update release process.

This is also what the autopkgtests run and now the mtr call is identical
to the one used in mariadb-10.3 packaging.

Related to https://jira.mariadb.org/browse/MDEV-21587