Bug#999569: systemd-logind: service does not start with only dbus-broker installed

[Christian Göttsche]

Package: systemd
Version: 249.6-1

In version 249.6-1 the dependency on dbus, e.g. in libpam-systemd, got
replaced by `default-dbus-system-bus | dbus-system-bus`.
This allows the dependency to be fulfilled by only dbus-broker and the
traditional dbus package to be removed.
The service file of systemd-logind contains the condition
`ConditionPathExists=/lib/systemd/system/dbus.service` resulting in
systemd-logind.service no being started.
As suggested on #IRC the following patch allows systemd-logind.service
to be started:

-ConditionPathExists=/lib/systemd/system/dbus.service
+ConditionPathExists=|/lib/systemd/system/dbus.service
+ConditionPathExists=|/lib/systemd/system/dbus-broker.service