Fixed failing testcase rename_table_debug

Test was missing a FLUSH TABLES

mysql-test/suite/innodb/r/rename_table_debug.result

+FLUSH TABLES;
 CREATE TABLE t1 (a SERIAL, b INT, c INT, d INT) ENGINE=InnoDB;
 INSERT INTO t1 () VALUES ();
 connect  con1,localhost,root,,test;

mysql-test/suite/innodb/t/rename_table_debug.test

@@ -3,6 +3,7 @@
 --source include/have_debug_sync.inc
 --source include/not_embedded.inc
 
+FLUSH TABLES;
 LET $datadir= `SELECT @@datadir`;
 
 CREATE TABLE t1 (a SERIAL, b INT, c INT, d INT) ENGINE=InnoDB;