Update mysql.go renamed groups to hstgrp due to zabbix change
Update mysql.go renamed groups to hstgrp due to zabbix change

Zabbix has changed the name of table groups to hstgrp due to key reservations in mysql 8
https://www.zabbix.com/forum/zabbix-help/374145-is-table-groups-on-mysql-missing-after-update-3-2-11-to-4-0-4
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