Fix DBUG_ENTER/return mismatch

Spotted by Thirunarayanan Balathandayuthapani.

storage/innobase/row/row0merge.cc

@@ -1092,7 +1092,7 @@ row_merge_read(
 	if (success && log_tmp_is_encrypted()) {
 		if (!log_tmp_block_decrypt(buf, srv_sort_buf_size,
 					   crypt_buf, ofs)) {
-			return (FALSE);
+			DBUG_RETURN(false);
 		}
 
 		srv_stats.n_merge_blocks_decrypted.inc();
@@ -1141,7 +1141,7 @@ row_merge_write(
 					   buf_len,
 					   static_cast<byte*>(crypt_buf),
 					   ofs)) {
-			return false;
+			DBUG_RETURN(false);
 		}
 
 		srv_stats.n_merge_blocks_encrypted.inc();