Inotify: write_network_interfaces : always autostart bond slaves interfaces

Inotify: write_network_interfaces : always autostart bond slaves interfaces

Currently, bond slaves are mostly working without autostart,
because bond slaves scripts from ifupdown1 && also ifupdown2
 have some kind of hacks to start the slaves.

But if users want to do some tuning on the ifaces, they are not applied.

Also, with ifupdown2 + ovs, this kind of hack is not implemented (yet), so the
slaves of the bond are still down.

Debian/Ubuntu official docs always set "auto ethX" for bond slaves,
it's really more clean like this.

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