Merge branch 'hotfix/3859' into 'stable-3.1'

fixed #3859

Bug fix for #3859, adding `class="form-control"` makes the box full-width. Same like the refresh box here:
https://git.ispconfig.org/ispconfig/ispconfig3/blob/master/interface/web/monitor/templates/show_sys_state.htm#L10

See merge request !407