routing: stop tracking totalAmount in paymentLifecycle

This commit removes the field `totalAmount` from `paymentLifecycle` and
only reads it from the channeldb payment.

routing/router.go

@@ -667,9 +667,8 @@ func (r *ChannelRouter) Start() error {
 			// also set a zero fee limit, as no more routes should
 			// be tried.
 			_, _, err := r.sendPayment(
-				payment.Info.Value, 0,
-				payment.Info.PaymentIdentifier, 0, paySession,
-				shardTracker,
+				0, payment.Info.PaymentIdentifier, 0,
+				paySession, shardTracker,
 			)
 			if err != nil {
 				log.Errorf("Resuming payment %v failed: %v.",
@@ -2048,7 +2047,7 @@ func (r *ChannelRouter) SendPayment(payment *LightningPayment) ([32]byte,
 	// Since this is the first time this payment is being made, we pass nil
 	// for the existing attempt.
 	return r.sendPayment(
-		payment.Amount, payment.FeeLimit, payment.Identifier(),
+		payment.FeeLimit, payment.Identifier(),
 		payment.PayAttemptTimeout, paySession, shardTracker,
 	)
 }
@@ -2071,7 +2070,7 @@ func (r *ChannelRouter) SendPaymentAsync(payment *LightningPayment) error {
 			spewPayment(payment))
 
 		_, _, err := r.sendPayment(
-			payment.Amount, payment.FeeLimit, payment.Identifier(),
+			payment.FeeLimit, payment.Identifier(),
 			payment.PayAttemptTimeout, paySession, shardTracker,
 		)
 		if err != nil {
@@ -2335,9 +2334,9 @@ func (r *ChannelRouter) sendToRoute(htlcHash lntypes.Hash, rt *route.Route,
 // carry out its execution. After restarts it is safe, and assumed, that the
 // router will call this method for every payment still in-flight according to
 // the ControlTower.
-func (r *ChannelRouter) sendPayment(
-	totalAmt, feeLimit lnwire.MilliSatoshi, identifier lntypes.Hash,
-	timeout time.Duration, paySession PaymentSession,
+func (r *ChannelRouter) sendPayment(feeLimit lnwire.MilliSatoshi,
+	identifier lntypes.Hash, timeout time.Duration,
+	paySession PaymentSession,
 	shardTracker shards.ShardTracker) ([32]byte, *route.Route, error) {
 
 	// We'll also fetch the current block height so we can properly
@@ -2351,7 +2350,6 @@ func (r *ChannelRouter) sendPayment(
 	// can resume the payment from the current state.
 	p := &paymentLifecycle{
 		router:        r,
-		totalAmount:   totalAmt,
 		feeLimit:      feeLimit,
 		identifier:    identifier,
 		paySession:    paySession,