lnwallet: add missed addition of RHash

add rhash to the payment descriptor when receiving the settle htlc in
order to be able to pass it during settle htlc packet generation and
later find the user pending payment by rhash without additional hashing.

lnwallet/channel.go

@@ -2251,6 +2251,7 @@ func (lc *LightningChannel) ReceiveHTLCSettle(preimage [32]byte, logIndex uint64
 		Amount:      htlc.Amount,
 		RPreimage:   preimage,
 		ParentIndex: htlc.Index,
+		RHash:       htlc.RHash,
 		Index:       lc.remoteUpdateLog.logIndex,
 		EntryType:   Settle,
 	}