OnCalendar expression in Summary Template is misformatted

In `sysstat_summary.timer.override.epp`, there is the format

```
[Timer]
OnCalendar=00:<%= $sa2_hour %>:<%= $sa2_minute %>
```

But the OnCalendar expression is hour:minute:second, so it should be

```
[Timer]
OnCalendar=<%= $sa2_hour %>:<%= $sa2_minute %>
```