...from the package and clean up the conffile on upgrades. We have the
dbus-user-session package in Debian to properly enable the D-Bus
user-session mode which also takes care of updating the systemd --user
environment.
Closes: #795761
Simon McVittie says that this needs to wait until Stretch+1 to avoid problems
on dist-upgrade due to policy files disappearing from /etc while the old
dbus-daemon is still running.
This reverts commit 5daf857c43.
Use 224-2 as version in rm_conffile because otherwise the file will be
removed on 224-2 => 225-1 upgrades, when the file is now the property of
systemd-container, not systemd.
Closes: #797048
