fix spider/bugfix.mdev_22979 test

* remove the file to be --repeat friendly
* specify the correct defaults-group-suffix. Spider doesn't use the
  conventional .1 group, so MYSQLD_CMD skips a lot of config options,
  in particular it doesn't read --tmpdir and creates files in /tmp

Author: vuvova

storage/spider/mysql-test/spider/bugfix/t/mdev_22979.test

@@ -12,7 +12,8 @@ let $PLUGIN_DIR=`select @@plugin_dir`;
 --write_file $MYSQLTEST_VARDIR/tmp/mdev_22979.sql
 drop table if exists foo.bar;
 EOF
---exec $MYSQLD_CMD --datadir=$MYSQLD_DATADIR --bootstrap --plugin-dir=$PLUGIN_DIR --plugin-load-add=ha_spider < $MYSQLTEST_VARDIR/tmp/mdev_22979.sql
+--exec $MYSQLD --defaults-group-suffix=.1.1 --defaults-file=$MYSQLTEST_VARDIR/my.cnf --datadir=$MYSQLD_DATADIR --bootstrap --plugin-dir=$PLUGIN_DIR --plugin-load-add=ha_spider < $MYSQLTEST_VARDIR/tmp/mdev_22979.sql
 --source include/start_mysqld.inc
 --disable_query_log
 --source ../../include/clean_up_spider.inc
+--remove_file $MYSQLTEST_VARDIR/tmp/mdev_22979.sql