itest: use ht.CreateSimpleNetwork whenever applicable

So we won't forget to assert the topology after opening a chain of
channels.

itest/lnd_quiescence_test.go

@@ -6,6 +6,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc/devrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/node"
 	"github.com/stretchr/testify/require"
 )
 
@@ -16,12 +17,14 @@ import (
 // NOTE FOR REVIEW: this could be improved by blasting the channel with HTLC
 // traffic on both sides to increase the surface area of the change under test.
 func testQuiescence(ht *lntest.HarnessTest) {
-	alice := ht.NewNodeWithCoins("Alice", nil)
-	bob := ht.NewNode("Bob", nil)
+	cfg := node.CfgAnchor
+	chanPoints, nodes := ht.CreateSimpleNetwork(
+		[][]string{cfg, cfg}, lntest.OpenChannelParams{
+			Amt: btcutil.Amount(1000000),
+		})
 
-	chanPoint := ht.OpenChannel(bob, alice, lntest.OpenChannelParams{
-		Amt: btcutil.Amount(1000000),
-	})
+	alice, bob := nodes[0], nodes[1]
+	chanPoint := chanPoints[0]
 
 	res := alice.RPC.Quiesce(&devrpc.QuiescenceRequest{
 		ChanId: chanPoint,