Fix race in test case.

mysql-test/r/myisam-metadata.result

@@ -5,7 +5,10 @@ a VARCHAR(100),
 INDEX(a)
 ) ENGINE=MyISAM;
 ALTER TABLE t1 DISABLE KEYS;
+SET debug_sync= 'myisam_after_repair_by_sort SIGNAL waiting WAIT_FOR go';
 ALTER TABLE t1 ENABLE KEYS;
+SET debug_sync= 'now WAIT_FOR waiting';
+SET debug_sync= 'now SIGNAL go';
 SHOW TABLE STATUS LIKE 't1';
 Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
 t1	MyISAM	10	Dynamic	100000	27	#	#	#	0	NULL	#	#	#	latin1_swedish_ci	NULL		

mysql-test/t/myisam-metadata.test

@@ -29,7 +29,8 @@ while ($1)
 --enable_query_log
 
 --connect(con1,localhost,root,,)
---send
+SET debug_sync= 'myisam_after_repair_by_sort SIGNAL waiting WAIT_FOR go';
+send
   ALTER TABLE t1 ENABLE KEYS;
 
 --connection default
@@ -38,6 +39,8 @@ while ($1)
 --let $field= State
 --let $condition= = 'Repair by sorting'
 --source include/wait_show_condition.inc
+SET debug_sync= 'now WAIT_FOR waiting';
+SET debug_sync= 'now SIGNAL go';
 
 --replace_column 7 # 8 # 9 # 12 # 13 # 14 #
 SHOW TABLE STATUS LIKE 't1';

storage/myisam/ha_myisam.cc

@@ -30,6 +30,7 @@
 #include "rt_index.h"
 #include "sql_table.h"                          // tablename_to_filename
 #include "sql_class.h"                          // THD
+#include "debug_sync.h"
 
 ulonglong myisam_recover_options;
 static ulong opt_myisam_block_size;
@@ -1131,6 +1132,7 @@ int ha_myisam::repair(THD *thd, HA_CHECK &param, bool do_optimize)
         thd_proc_info(thd, "Repair by sorting");
         error = mi_repair_by_sort(&param, file, fixed_name,
                                   test(param.testflag & T_QUICK));
+        DEBUG_SYNC(thd, "myisam_after_repair_by_sort");
       }
     }
     else