protected close_cached_table() call in REPAIR ... USE_FRM with a mutex

test for REPAIR ... USE_FRM added

mysql-test/r/repair.result

+drop table if exists t1;
+create table t1 SELECT 1,"table 1";
+repair table t1 use_frm;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	warning	Number of rows changed from 0 to 1
+test.t1	repair	status	OK
+drop table if exists t1;

mysql-test/t/repair.test

+#
+# Test of repair table
+#
+
+drop table if exists t1;
+create table t1 SELECT 1,"table 1";
+repair table t1 use_frm;
+drop table if exists t1;

sql/sql_table.cc

@@ -972,7 +972,9 @@ static int prepare_for_repair(THD* thd, TABLE_LIST* table,
     fn_format(from, from, "", MI_NAME_DEXT, 4);
     sprintf(tmp,"%s-%lx_%lx", from, current_pid, thd->thread_id);
 
+    pthread_mutex_lock(&LOCK_open);
     close_cached_table(thd,table->table);
+    pthread_mutex_unlock(&LOCK_open);
 
     if (lock_and_wait_for_table_name(thd,table))
       DBUG_RETURN(-1);