MT#9615 Ship default /etc/network/interfaces file using DHCP

We're customizing /e/n/i in our ngcp installations anyway
after [grml-]deboostrapping the installation via deployment.sh.
But when installing plain Debian systems we depend on a working
/e/n/i file, which isn't true yet because recently we get the
/e/n/i file copied from the host to the installed system which
doesn't work there then as-is.

Depend on grml-deboostrap v0.67 even though the
--defaultinterfaces option was introduced in v0.64,
but v0.67 is what's targeted for Debian/jessie as well
as the upcoming Grml stable release and we're using that
version already anyway because it's the one present in
the grml-testing repository.

Change-Id: Id48636a16cce25fc6a52b6fcaa3db828b9459484

deployment.sh

@@ -189,7 +189,7 @@ fai_upgrade() {
 }
 
 grml_debootstrap_upgrade() {
-  local required_version=0.62
+  local required_version=0.67
   local present_version=$(dpkg-query --show --showformat='${Version}' grml-debootstrap)
 
   if dpkg --compare-versions $present_version lt $required_version ; then
@@ -1152,6 +1152,7 @@ echo y | grml-debootstrap \
   --mirror "$MIRROR" \
   --debopt "--keyring=${KEYRING}" $EXTRA_DEBOOTSTRAP_OPTS \
   --keep_src_list \
+  --defaultinterfaces \
   -r "$DEBIAN_RELEASE" \
   -t "$ROOT_FS" \
   --password 'sipwise' 2>&1 | tee -a /tmp/grml-debootstrap.log