routing: rename mock structs to make them obsolete

This commit renames the mock structs by appending Old in their names. In
doing so the old tests stay unchanged and new mock structs can be added
in the following commit.

routing/payment_lifecycle_test.go

@@ -739,7 +739,7 @@ func testPaymentLifecycle(t *testing.T, test paymentLifecycleTestCase,
 		sendResult := make(chan error)
 		paymentResult := make(chan *htlcswitch.PaymentResult)
 
-		payer := &mockPayer{
+		payer := &mockPayerOld{
 			sendResult:    sendResult,
 			paymentResult: paymentResult,
 		}
@@ -749,8 +749,8 @@ func testPaymentLifecycle(t *testing.T, test paymentLifecycleTestCase,
 			Chain:              chain,
 			ChainView:          chainView,
 			Control:            control,
-			SessionSource:      &mockPaymentSessionSource{},
-			MissionControl:     &mockMissionControl{},
+			SessionSource:      &mockPaymentSessionSourceOld{},
+			MissionControl:     &mockMissionControlOld{},
 			Payer:              payer,
 			ChannelPruneExpiry: time.Hour * 24,
 			GraphPruneInterval: time.Hour * 2,
@@ -822,12 +822,12 @@ func testPaymentLifecycle(t *testing.T, test paymentLifecycleTestCase,
 	// Setup our payment session source to block on release of
 	// routes.
 	routeChan := make(chan struct{})
-	router.cfg.SessionSource = &mockPaymentSessionSource{
+	router.cfg.SessionSource = &mockPaymentSessionSourceOld{
 		routes:       test.routes,
 		routeRelease: routeChan,
 	}
 
-	router.cfg.MissionControl = &mockMissionControl{}
+	router.cfg.MissionControl = &mockMissionControlOld{}
 
 	// Send the payment. Since this is new payment hash, the
 	// information should be registered with the ControlTower.