Don't configure the eth0 interface by default

In xenial, eth0 won't exist (as we've moved to systemd's predictable interface
naming), and even were it to exist, cloud-init would handle configuring it on
boot.

live-build/ubuntu-cpc/includes.chroot/etc/network/interfaces

@@ -8,8 +8,5 @@ iface lo inet loopback
 # Source interfaces
 # Please check /etc/network/interfaces.d before changing this file
 # as interfaces may have been defined in /etc/network/interfaces.d
-# NOTE: the primary ethernet device is defined in
-# /etc/network/interfaces.d/eth0
 # See LP: #1262951
 source /etc/network/interfaces.d/*.cfg
-

live-build/ubuntu-cpc/includes.chroot/etc/network/interfaces.d/eth0.cfg

@@ -1,3 +0,0 @@
-# The primary network interface
-auto eth0
-iface eth0 inet dhcp