rpcserver: return the plain reject reason from btcd

This commit changes the `RejectReason` resulted from calling
btcd's `testmempoolaccept` to be un-matched, leaving it to the caller to
decide when and where to match it.

rpcserver.go

@@ -39,7 +39,6 @@ import (
 	"github.com/btcsuite/btcd/mining"
 	"github.com/btcsuite/btcd/mining/cpuminer"
 	"github.com/btcsuite/btcd/peer"
-	"github.com/btcsuite/btcd/rpcclient"
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/websocket"
@@ -3858,9 +3857,7 @@ func handleTestMempoolAccept(s *rpcServer, cmd interface{},
 
 			// TODO(yy): differentiate the errors and put package
 			// error in `PackageError` field.
-			item.RejectReason = rpcclient.MapBtcdErrToRejectReason(
-				err,
-			)
+			item.RejectReason = err.Error()
 
 			results = append(results, item)