Backup compat tests use 'test-' prefix (as it was initially for all the
tests. Since changing this right not may break those backups in
non-trivial way, simply add cleanup for 'test-*' VMs.
sfdisk options and input format differs between versions (dropped MB
units support), so instead of supporting all the combinations,
simply paste its result verbatim.
Test suite now logs to three places:
* syslog
* ${HOME}/qubes-tests.log
* /dev/kmsg (only start and errors; this is handy while debugging Oopses by
correlating them with tests)
