driver/name_owner_changed: generate the unique name if no name is given
driver/name_owner_changed: generate the unique name if no name is given

If NULL is passed in instead of the name, take the name to be the unique
name of (the only) peer that was passed in. This is only used for the
initial NameAcquired and the final NameLost.

Signed-off-by: Tom Gundersen <7c8224529a7c718e876cb2496c973509fde1e50e@jklm.no>

bus1/dbus-broker