Bug#21847100 HANDLER ROLLBACK VARIABLE VALUE FOR DELTA AND HOST DIFFERS IN PS AND IS

MTR invokes preliminary checks that affect the starting value of
the status counters. These status counts differ between I_S and
P_S because of the different code paths taken for SHOW commands.

The testcase measures only the status count deltas, not the starting
values. To avoid any discrepancies, between I_S and P_S, the
test now performs FLUSH STATUS to clear beginning status counts.

Author: Christopher Powers

mysql-test/suite/perfschema/t/show_aggregate.test

@@ -26,6 +26,12 @@ SET @@session.sql_log_bin=OFF;
 --echo # CREATE 3 CLIENTS, 3 CONNECTIONS, RESULTS TABLE
 connection default;
 USE test;
+
+# Clear user, host and account status accumulated from preliminary checks by mtr.
+--disable_query_log
+flush status;
+--enable_query_log
+
 --echo
 --echo # Create results table
 CREATE TABLE test.status_results