Satoshi amounts must be used for htlc comparison

[pm47]

Spec says that the equality is based on outputs, which are in sats:

Lexicographic ordering: see BIP69. In the case of identical HTLC outputs, the outputs are ordered in increasing cltv_expiry order.

We're using the millisatoshi amount:

eclair/eclair-core/src/main/scala/fr/acinq/eclair/transactions/Transactions.scala

Lines 309 to 314 in 898c17b

	def sort(a: CommitmentOutputLink[CommitmentOutput], b: CommitmentOutputLink[CommitmentOutput]): Boolean = (a.commitmentOutput, b.commitmentOutput) match {
	case (OutHtlc(OutgoingHtlc(htlcA)), OutHtlc(OutgoingHtlc(htlcB))) if htlcA.paymentHash == htlcB.paymentHash && htlcA.amountMsat == htlcB.amountMsat =>
	htlcA.cltvExpiry <= htlcB.cltvExpiry
	case _ => LexicographicalOrdering.isLessThan(a.output, b.output)
	}
	}

This causes commitment sig mismatch and force closes.

Thanks @Roasbeef for the debug!

[pm47]

Related to lightning/bolts#872.