sweep+contractcourt: track best height in UtxoSweeper

Thus we can use shorter method signatures. In doing so we also remove an
old TODO in one use case of `CreateSweepTx`.

contractcourt/commit_sweep_resolver_test.go

@@ -140,8 +140,8 @@ func (s *mockSweeper) SweepInput(input input.Input, params sweep.Params) (
 	return result, nil
 }
 
-func (s *mockSweeper) CreateSweepTx(inputs []input.Input, feePref sweep.FeePreference,
-	currentBlockHeight uint32) (*wire.MsgTx, error) {
+func (s *mockSweeper) CreateSweepTx(inputs []input.Input,
+	feePref sweep.FeePreference) (*wire.MsgTx, error) {
 
 	// We will wait for the test to supply the sweep tx to return.
 	sweepTx := <-s.createSweepTxChan

contractcourt/htlc_success_resolver.go

@@ -432,17 +432,13 @@ func (h *htlcSuccessResolver) resolveRemoteCommitOutput() (
 		// transaction, that we'll use to move these coins back into
 		// the backing wallet.
 		//
-		// TODO: Set tx lock time to current block height instead of
-		// zero. Will be taken care of once sweeper implementation is
-		// complete.
-		//
 		// TODO: Use time-based sweeper and result chan.
 		var err error
 		h.sweepTx, err = h.Sweeper.CreateSweepTx(
 			[]input.Input{inp},
 			sweep.FeePreference{
 				ConfTarget: sweepConfTarget,
-			}, 0,
+			},
 		)
 		if err != nil {
 			return nil, err

contractcourt/interfaces.go

@@ -53,8 +53,8 @@ type UtxoSweeper interface {
 	// CreateSweepTx accepts a list of inputs and signs and generates a txn
 	// that spends from them. This method also makes an accurate fee
 	// estimate before generating the required witnesses.
-	CreateSweepTx(inputs []input.Input, feePref sweep.FeePreference,
-		currentBlockHeight uint32) (*wire.MsgTx, error)
+	CreateSweepTx(inputs []input.Input,
+		feePref sweep.FeePreference) (*wire.MsgTx, error)
 
 	// RelayFeePerKW returns the minimum fee rate required for transactions
 	// to be relayed.