fixup! blockchain, netsync, main, cmd/addblock: Use utxocache

blockchain/chain.go

@@ -1188,9 +1188,12 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 		// to the main chain without violating any rules and without
 		// actually connecting the block.
 		if !fastAdd {
-			// We create a viewpoint here to avoid mutating the utxo cache.
-			// The block is not considered valid until checkconnectblock
-			// returns and the mutation would force us to undo the cache.
+			// We create a viewpoint here to avoid spending or adding new
+			// coins to the utxo cache.
+			//
+			// checkConnectBlock spends and adds utxos before doing the
+			// signature validation and if the signature validation fails,
+			// we would be forced to undo the utxo cache.
 			//
 			// TODO (kcalvinalvin): Doing all of the validation before connecting
 			// the tx inside check connect block would allow us to pass the utxo