BUG#25256910: NODE RECOVERY FAILS WITH ERROR_CODE: 1062; HANDLER ERROR HA_ERR_FOUND_DUPP_KEY [Post-Fix]

Failures were detected on weekly-5.7 failing the execution of DROP TABLE t1.

An explanation for this problem is that at the end of the test we start the
server 2 applier again. The applier has a transaction to apply on t1 but we
never check if it is already applied or not.

In the end of the test we also do a drop on table t1, that in theory could be
certified and executed sooner than the remote transaction on t1.

So it was added a wait condition to confirm the presence of the data on
server2.

Author: Anibal Pinto

rapid/plugin/group_replication/tests/mtr/t/gr_single_primary_double_change.test

@@ -140,6 +140,10 @@ INSERT INTO t1 VALUES(1,2);
 
 --source ../inc/gr_start_applier_sql_thread.inc
 
+#Waiting for the data to be applied
+--let $wait_condition= SELECT COUNT(*)=1 FROM t1
+--source include/wait_condition.inc
+
 --let $negatively_certified= query_get_value(SELECT Count_conflicts_detected FROM performance_schema.replication_group_member_stats, Count_conflicts_detected, 1)
 --let $assert_text= 'The value of Count_conflicts_detected should be 1 on server 2'
 --let $assert_cond= $negatively_certified = 1