multi: enforce routing.MinCLTVDelta=18 for invoices + chanupd

This commit clamps all user-chosen CLTVs in LND to be at least 18, which
is the new conservative value used in the sepc. This minimum is applied
uniformly to forwarding CLTV deltas (via channel updates) as well as
final CLTV deltas for new invoices.

routing/router_test.go

@@ -23,7 +23,6 @@ import (
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/routing/route"
-	"github.com/lightningnetwork/lnd/zpay32"
 )
 
 var uniquePaymentID uint64 = 1 // to be used atomically
@@ -223,7 +222,7 @@ func TestFindRoutesWithFeeLimit(t *testing.T) {
 	route, err := ctx.router.FindRoute(
 		ctx.router.selfNode.PubKeyBytes,
 		target, paymentAmt, restrictions, nil, nil,
-		zpay32.DefaultFinalCLTVDelta,
+		MinCLTVDelta,
 	)
 	if err != nil {
 		t.Fatalf("unable to find any routes: %v", err)
@@ -1284,7 +1283,7 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 	_, err = ctx.router.FindRoute(
 		ctx.router.selfNode.PubKeyBytes,
 		targetPubKeyBytes, paymentAmt, noRestrictions, nil, nil,
-		zpay32.DefaultFinalCLTVDelta,
+		MinCLTVDelta,
 	)
 	if err != nil {
 		t.Fatalf("unable to find any routes: %v", err)
@@ -1327,7 +1326,7 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 	_, err = ctx.router.FindRoute(
 		ctx.router.selfNode.PubKeyBytes,
 		targetPubKeyBytes, paymentAmt, noRestrictions, nil, nil,
-		zpay32.DefaultFinalCLTVDelta,
+		MinCLTVDelta,
 	)
 	if err != nil {
 		t.Fatalf("unable to find any routes: %v", err)