cln: uses the exact channel to probe payment

To ensures that the invoice payment is probed
via the direct channel to the peer.

clightning/clightning.go

@@ -640,17 +640,23 @@ func (cl *ClightningClient) ProbePayment(scid string, amountMsat uint64) (bool,
 		}
 	}
 
-	route, err := cl.glightning.GetRoute(channel.PeerId, amountMsat, 1, 0, cl.nodeId, 0, nil, 1)
-	if err != nil {
-		return false, "", fmt.Errorf("GetRoute() %w", err)
-	}
 	preimage, err := lightning.GetPreimage()
 	if err != nil {
 		return false, "", fmt.Errorf("GetPreimage() %w", err)
 	}
 	paymentHash := preimage.Hash().String()
 	_, err = cl.glightning.SendPay(
-		route,
+		[]glightning.RouteHop{
+			{
+				Id:             channel.PeerId,
+				ShortChannelId: scid,
+				AmountMsat:     glightning.AmountFromMSat(amountMsat),
+				// The total expected CLTV.
+				// The default GetRoute value of 9 is set here.
+				Delay:     9,
+				Direction: 0,
+			},
+		},
 		paymentHash,
 		"",
 		amountMsat,