itest: remove the use of standby nodes

This commit removes the usage of the standby nodes and uses
`CreateSimpleNetwork` when applicable. Also introduces a helper method
`NewNodeWithCoins` to quickly start a node with funds.

itest/lnd_multi-hop-payments_test.go

@@ -18,7 +18,8 @@ func testMultiHopPayments(ht *lntest.HarnessTest) {
 	// channel with Alice, and Carol with Dave. After this setup, the
 	// network topology should now look like:
 	//     Carol -> Dave -> Alice -> Bob
-	alice, bob := ht.Alice, ht.Bob
+	alice := ht.NewNodeWithCoins("Alice", nil)
+	bob := ht.NewNode("Bob", nil)
 
 	daveArgs := []string{"--protocol.legacy.onion"}
 	dave := ht.NewNode("Dave", daveArgs)
@@ -37,6 +38,7 @@ func testMultiHopPayments(ht *lntest.HarnessTest) {
 	ht.AssertHtlcEventType(daveEvents, routerrpc.HtlcEvent_UNKNOWN)
 
 	// Connect the nodes.
+	ht.ConnectNodes(alice, bob)
 	ht.ConnectNodes(dave, alice)
 	ht.ConnectNodes(carol, dave)