functional: remove workarounds for fixed bugs
functional: write out sshd_config to skip DNS reverse lookup
Merge pull request #685 from bcwaldon/functional-no-ssh-dns

Manually prevent reverse DNS lookup in nspawn sshd
functional: add PoweroffMember method
functional: wait for machine to shut down
functional: ignore error from systemctl status

The error object does not matter for the test, and the behavior
of systemd seems to have changed recently. Just ignore it.
functional: fix logic in test