when the host has ifupdown2 installed, we can hot apply the config
add a button to do this
if the user does not meet the requirements, the api call
will show why and throw an error (without changing anything)
the button has to be enabled via 'showApplyBtn', because for now,
we do not want it for pmg
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>