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/reservation.go

@@ -155,6 +155,8 @@ func NewChannelReservation(capacity, fundingAmt btcutil.Amount, minFeeRate btcut
 		initiator    bool
 	)
 
+	commitFee := minFeeRate * commitWeight / 1000
+
 	// If we're the responder to a single-funder reservation, then we have
 	// no initial balance in the channel unless the remote party is pushing
 	// some funds to us within the first commitment state.
@@ -166,20 +168,22 @@ func NewChannelReservation(capacity, fundingAmt btcutil.Amount, minFeeRate btcut
 		// TODO(roasbeef): need to rework fee structure in general and
 		// also when we "unlock" dual funder within the daemon
 
-		if capacity == fundingAmt+commitFee {
+		if capacity == fundingAmt {
 			// If we're initiating a single funder workflow, then
 			// we pay all the initial fees within the commitment
 			// transaction. We also deduct our balance by the
 			// amount pushed as part of the initial state.
 			ourBalance = capacity - commitFee - pushSat
+			theirBalance = capacity - fundingAmt + pushSat
 		} else {
 			// Otherwise, this is a dual funder workflow where both
 			// slides split the amount funded and the commitment
 			// fee.
-			ourBalance = fundingAmt - commitFee
+			ourBalance = fundingAmt - (commitFee / 2)
+			theirBalance = capacity - fundingAmt -
+				(commitFee / 2) + pushSat
 		}
 
-		theirBalance = capacity - fundingAmt - commitFee + pushSat
 		initiator = true
 	}