add a forgotten debug sync point, that a test case was referring to

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

@@ -13,7 +13,7 @@ INSERT INTO t1(k) VALUES (1), (2), (3) ON DUPLICATE KEY UPDATE c='1';
 #
 # Connection 2
 #
-SET DEBUG_SYNC='start_ha_write_row WAIT_FOR continue2';
+SET DEBUG_SYNC='ha_write_row_start WAIT_FOR continue2';
 affected rows: 0
 SET DEBUG_SYNC='after_mysql_insert SIGNAL continue1';
 affected rows: 0

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

@@ -33,7 +33,7 @@ SET DEBUG_SYNC='ha_write_row_end SIGNAL continue2 WAIT_FOR continue1';
 --echo #
 --echo # Connection 2
 --echo #
-SET DEBUG_SYNC='start_ha_write_row WAIT_FOR continue2';
+SET DEBUG_SYNC='ha_write_row_start WAIT_FOR continue2';
 SET DEBUG_SYNC='after_mysql_insert SIGNAL continue1';
 INSERT INTO t1(k) VALUES (2), (4), (5) ON DUPLICATE KEY UPDATE c='2';
 

sql/handler.cc

@@ -5335,6 +5335,7 @@ int handler::ha_write_row(uchar *buf)
   int error;
   Log_func *log_func= Write_rows_log_event::binlog_row_logging_function;
   DBUG_ENTER("handler::ha_write_row");
+  DEBUG_SYNC_C("ha_write_row_start");
 
   /* If we have a timestamp column, update it to the current time */
   if (table->timestamp_field_type & TIMESTAMP_AUTO_SET_ON_INSERT)