I made a diff between systemd-sysv 215-17+deb8u5 (bug not present) and 215-17+deb8u7 (bug present), and there are 2 new patches (introduced in version 215-17+deb8u6) that may be related to this bug:
* systemctl-fix-argument-handling-when-invoked-as-shutdown.patch * systemctl-when-reading-legacy-t-argument-for-shutdown-don.patch
