quarantine: improve borders for docked items

quarantine: improve borders for docked items

one cannot set the different borders seperately in panels/grids and
docked items don't have a bottom border in extjs, but we want to remove
all borders except the ones between the toolbar and the grids/content
below that.

to achieve that, set a custom 'border-bottom-width' with '!important'
(extjs has a rule with !important as well) for the toolbar, and
everywhere else remove the border.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>