sd-bus: destination-matches cannot match NameOwnerChanged

Make sure we don't install NameOwnerChanged matches if the caller passed
a destination='' match (except if it is the broadcast address). Per spec,
all NameOwnerChanged signals are broadcasts.

Only the NameLost/NameAcquired signals are unicasts, but those are never
received through sd-bus. Instead, the bus-proxy synthesizes them and it
already installs proper matches for them.

src/libsystemd/sd-bus/bus-control.c

@@ -1345,6 +1345,10 @@ int bus_add_match_internal_kernel(
                         else if (r > 0)
                                 sz += ALIGN8(offsetof(struct kdbus_item, id) + sizeof(uint64_t));
 
+                        /* if not a broadcast, it cannot be a name-change */
+                        if (r <= 0 || dst_id != KDBUS_DST_ID_BROADCAST)
+                                matches_name_change = false;
+
                         break;
                 }