In kdbus we still have to support org.freedesktop.DBus matches even though
there is no real bus driver. The reason is that bus-control.c turns
NameOwnerChanged matches into proper kdbus matches. If we drop DRIVER
matches early, we will never match on name-changes for kdbus.
Two ways to fix this:
1) Install DRIVER matches on kdbus (which is the simple way our and which
is what this patch does).
2) Properly fix the scope-detection to let NameOwnerChanged matches
through (or better: block anything with Member!=NameOwnerChanged).
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