Addendum to bug #30263773: fix the test suite to sustain nonempty --secure-file-priv default value

RB#23405

Extended the test arguments so they actually test the real fix.
Added the --secure-file-priv="" default for the test to operate on.

Author: gkodinov

mysql-test/t/persisted_variables_bugs_fast.test

@@ -7,11 +7,11 @@
 
 --echo # Must contain an error about failing to set a data dir
 --error 1
---exec $MYSQLD --no-defaults --datadir =x > $LOG_FILE 2>&1
+--exec $MYSQLD --no-defaults --secure-file-priv="" --datadir =xyz > $LOG_FILE 2>&1
 
 --let $assert_file = $LOG_FILE
 --let $assert_text = error log must contain failed to set data dir error
---let $assert_select = \[ERROR\] \[MY-[0-9][0-9]*\] \[Server\] Failed to set datadir to .*=x.*
+--let $assert_select = \[ERROR\] \[MY-[0-9][0-9]*\] \[Server\] Failed to set datadir to .*=xyz.*
 --let $assert_count = 1
 --source include/assert_grep.inc