Make rd_debug aligned to var-tx

Fix the corner case and use the right rate cost udpate for rd_debug.
This would make the var-tx pass rd_debug test.

Change-Id: Ib0fbd2d73030c0d150222c6b7c2dfffc0c6af085
diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 0c7eea1..d0f0b99 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -3344,6 +3344,10 @@
              RDCOST(x->rdmult, x->rddiv, zero_blk_rate, rd_stats->sse) ||
          rd_stats->skip == 1) &&
         !xd->lossless[mbmi->segment_id]) {
+#if CONFIG_RD_DEBUG
+      av1_update_txb_coeff_cost(rd_stats, plane, tx_size, blk_row, blk_col,
+                                zero_blk_rate - rd_stats->rate);
+#endif
       rd_stats->rate = zero_blk_rate;
       rd_stats->dist = rd_stats->sse;
       rd_stats->skip = 1;