Fix an enc/dec mismatch issue in tokenization

Resolve an enc/dec mismatch issue in new-tokenset and var-tx.

BUG=aomedia:567

Change-Id: I9bd8ec4c7716bca3a5e551b6e9838fc8ef37f198
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 94b5bed..0a6e83c 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -855,6 +855,9 @@
     if (token == BLOCK_Z_TOKEN) {
       aom_write_symbol(w, 0, *p->head_cdf, HEAD_TOKENS + 1);
       p++;
+#if CONFIG_VAR_TX
+      break;
+#endif
       continue;
     }