INotify: remove allow-hotplug from /etc/network/interfaces

INotify: remove allow-hotplug from /etc/network/interfaces

for user installing proxmox on top of debian,
debian install by default the first nic with allow-hotplug.

This is conflicting with "auto ...", but worst with ovs "allow-ovs ...".

User have reported race with ovs, where ovs vmbr was up before the nic.
https://forum.proxmox.com/threads/no-network-on-server-unless-i-ifdown-ifup-vmbr0.62733/

Signed-off-by: Alexandre Derumier <aderumier@odiso.com>