One bus: the AMQP transport is gone from the host

The mesh runs on the seat's bus alone (novox/hq ADR 0131, design 28 task 5.5). The host's old
dialling and enrolment paths are deleted with the switch that chose between them; a membership or
a token naming another bus is refused before anything is sent, rather than dialled on a transport
that no longer exists.

cmd/mesh-host/main.go

@@ -1433,10 +1433,6 @@ func adoptDeliveredMembership(identityPath string, mine *identity.Identity, say
 		say(fmt.Sprintf("a membership for another bus was delivered and could not be saved: %v", err))
 		return
 	}
-	transport := next.Transport
-	if transport == "" {
-		transport = "the current"
-	}
-	say(fmt.Sprintf("moving to %s bus at %s — restarting to dial it", transport, next.Broker))
+	say(fmt.Sprintf("moving to the %s bus at %s — restarting to dial it", next.Transport, next.Broker))
 	os.Exit(0)
 }