peer: update cooperative closure unit tests to latest negotiation policy

With the new negotiation policy, we instead just need to ensure that
our fee inches closer to the other party’s with each iteration, and
that it’s within the proper bounds.

breacharbiter.go

@@ -1132,8 +1132,13 @@ func (b *breachArbiter) sweepSpendableOutputsTxn(txWeight uint64,
 		totalAmt += input.Amount()
 	}
 
-	feePerWeight := b.cfg.Estimator.EstimateFeePerWeight(1)
-	txFee := btcutil.Amount(txWeight * feePerWeight)
+	// We'll actually attempt to target inclusion within the next two
+	// blocks as we'd like to sweep these funds back into our wallet ASAP.
+	feePerWeight, err := b.cfg.Estimator.EstimateFeePerWeight(2)
+	if err != nil {
+		return nil, err
+	}
+	txFee := btcutil.Amount(txWeight * uint64(feePerWeight))
 
 	sweepAmt := int64(totalAmt - txFee)