lnwallet: replace hard-coded fees and adjust tests accordingly

This commit replaces the hard-coded 5000 satoshi fees with calls to the
FeeEstimator interface. This should provide a way to cleanly plug in
additional fee calculation algorithms in the future. This change
affected quite a few tests. When possible, the tests were changed to
assert amounts sent rather than balances so that fees wouldn't need to
be taken into account. There were several tests for which this wasn't
possible, so calls to the static fee calculator were made.

lnwallet/wallet.go

@@ -37,7 +37,8 @@ const (
 	// rotations, etc.
 	identityKeyIndex = hdkeychain.HardenedKeyStart + 2
 
-	commitFee = 5000
+	commitWeight = btcutil.Amount(724)
+	htlcWeight   = 172
 )
 
 var (
@@ -526,8 +527,7 @@ func (l *LightningWallet) handleFundingReserveRequest(req *initFundingReserveMsg
 	}
 
 	id := atomic.AddUint64(&l.nextFundingID, 1)
-	totalCapacity := req.capacity + commitFee
-	reservation := NewChannelReservation(totalCapacity, req.fundingAmount,
+	reservation := NewChannelReservation(req.capacity, req.fundingAmount,
 		req.minFeeRate, l, id, req.numConfs, req.pushSat)
 
 	// Grab the mutex on the ChannelReservation to ensure thread-safety
@@ -551,9 +551,8 @@ func (l *LightningWallet) handleFundingReserveRequest(req *initFundingReserveMsg
 	if req.fundingAmount != 0 {
 		// TODO(roasbeef): consult model for proper fee rate on funding
 		// tx
-		feeRate := uint64(10)
-		amt := req.fundingAmount + commitFee
-		err := l.selectCoinsAndChange(feeRate, amt, ourContribution)
+		err := l.selectCoinsAndChange(uint64(req.minFeeRate),
+			req.fundingAmount, ourContribution)
 		if err != nil {
 			req.err <- err
 			req.resp <- nil