invoices: use lntypes.Hash and lntypes.Preimage

Previously chainhash.Hash was used, which converts to/from string in
reversed format. Payment hashes and preimages are supposed to be
non-reversed.

htlcswitch/link.go

@@ -9,7 +9,6 @@ import (
 	"sync/atomic"
 	"time"
 
-	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/davecgh/go-spew/spew"
 	"github.com/go-errors/errors"
 	"github.com/lightningnetwork/lnd/channeldb"
@@ -17,6 +16,7 @@ import (
 	"github.com/lightningnetwork/lnd/htlcswitch/hodl"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnpeer"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/ticker"
@@ -2312,7 +2312,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 			// We're the designated payment destination.  Therefore
 			// we attempt to see if we have an invoice locally
 			// which'll allow us to settle this htlc.
-			invoiceHash := chainhash.Hash(pd.RHash)
+			invoiceHash := lntypes.Hash(pd.RHash)
 			invoice, minCltvDelta, err := l.cfg.Registry.LookupInvoice(
 				invoiceHash,
 			)