rpl_semi_sync_after_sync_row result mismatch

the failure signature is different from MDEV-14366:
CURRENT_TEST: rpl.rpl_semi_sync_after_sync_row
— /usr/share/mysql-test/suite/rpl/r/rpl_semi_sync_after_sync_row.result 2019-11-11 14:39:59.000000000 +0000
+++ /dev/shm/var/3/log/rpl_semi_sync_after_sync_row.reject 2019-11-11 16:03:20.590071576 +0000
@@ -407,7 +407,7 @@
[ Semi-sync status on master should be ON ]
show status like 'Rpl_semi_sync_master_clients';
Variable_name Value
-Rpl_semi_sync_master_clients 0
+Rpl_semi_sync_master_clients 1
show status like 'Rpl_semi_sync_master_status';
Variable_name Value
Rpl_semi_sync_master_status ON

The most probable reason is no synchronization of the master dump thread exit in the test.