Code review comment for ~mwhudson/curtin:lp-1893818

I ran the new vmtest but it failed across all the releases:

https://jenkins.ubuntu.com/server/job/curtin-vmtest-devel-debug/222/console

but I don't know if that's really a useful failure, as running the test_multipath.py tests from master also failed:

cmd: nosetests3 --process-timeout=86400 --processes=4 -vv --nologcapture tests/vmtests/test_multipath.py

console log: https://jenkins.ubuntu.com/server/job/curtin-vmtest-devel-debug/221/console
copypaste here: https://paste.ubuntu.com/p/HTp4xh2qYH/