multi: Add decayedlog db migration code

This commit adds the migration code for the decayedlog db which
is optional and will default to true.

channeldb/log.go

@@ -12,6 +12,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb/migration31"
 	"github.com/lightningnetwork/lnd/channeldb/migration32"
 	"github.com/lightningnetwork/lnd/channeldb/migration33"
+	"github.com/lightningnetwork/lnd/channeldb/migration34"
 	"github.com/lightningnetwork/lnd/channeldb/migration_01_to_11"
 	"github.com/lightningnetwork/lnd/kvdb"
 )
@@ -46,5 +47,6 @@ func UseLogger(logger btclog.Logger) {
 	migration31.UseLogger(logger)
 	migration32.UseLogger(logger)
 	migration33.UseLogger(logger)
+	migration34.UseLogger(logger)
 	kvdb.UseLogger(logger)
 }