network: use std remove button for confirm

network: use std remove button for confirm

alows to make the code simpler too, but we need to instantiate the
selection model explicitly, as we use a bit of a weird layout here to
be able to show the pending changes at the bottom, if any, so the
main gridpanel is not the parent of the toolbar buttons, so the
std-remove button does not automatically finds the selection model
when searching in the parent

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>