routing: use absolute final expiry in pathfinding

routing/heap.go

@@ -24,9 +24,10 @@ type nodeWithDist struct {
 	// amount that includes also the fees for subsequent hops.
 	amountToReceive lnwire.MilliSatoshi
 
-	// incomingCltv is the expected cltv value for the incoming htlc of this
-	// node. This value does not include the final cltv.
-	incomingCltv uint32
+	// incomingCltv is the expected absolute expiry height for the incoming
+	// htlc of this node. This value should already include the final cltv
+	// delta.
+	incomingCltv int32
 
 	// probability is the probability that from this node onward the route
 	// is successful.