routing: add chans rejected due to failed chain validation to zombie index

In this commit, we start to add any channels that fail the normal chain
validation to the zombie index. With this change, we'll ensure that we
won't continue to re-process the same set of spent channels over and
over again.

Fixes #5191.

routing/notifications_test.go

@@ -19,6 +19,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/chainview"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -170,8 +171,8 @@ func (m *mockChain) GetBlockHash(blockHeight int64) (*chainhash.Hash, error) {
 
 	hash, ok := m.blockIndex[uint32(blockHeight)]
 	if !ok {
-		return nil, fmt.Errorf("can't find block hash, for "+
-			"height %v", blockHeight)
+		return nil, fmt.Errorf("block number out of range: %v",
+			blockHeight)
 	}
 
 	return &hash, nil
@@ -182,6 +183,13 @@ func (m *mockChain) addUtxo(op wire.OutPoint, out *wire.TxOut) {
 	m.utxos[op] = *out
 	m.Unlock()
 }
+
+func (m *mockChain) delUtxo(op wire.OutPoint) {
+	m.Lock()
+	delete(m.utxos, op)
+	m.Unlock()
+}
+
 func (m *mockChain) GetUtxo(op *wire.OutPoint, _ []byte, _ uint32,
 	_ <-chan struct{}) (*wire.TxOut, error) {
 	m.RLock()
@@ -189,7 +197,7 @@ func (m *mockChain) GetUtxo(op *wire.OutPoint, _ []byte, _ uint32,
 
 	utxo, ok := m.utxos[*op]
 	if !ok {
-		return nil, fmt.Errorf("utxo not found")
+		return nil, btcwallet.ErrOutputSpent
 	}
 
 	return &utxo, nil