deployment: make sure MAC address for internal and external device are different

From: Michael Prokop <mprokop@sipwise.com>

deployment.sh

@@ -844,6 +844,11 @@ if "$PRO_EDITION" && [[ $(imvirt) != "Physical" ]] ; then
   INT_MAC=$(udevadm info -a -p /sys/class/net/${INTERNAL_DEV} | awk -F== '/ATTR{address}/ {print $2}')
   EXT_MAC=$(udevadm info -a -p /sys/class/net/${EXTERNAL_DEV} | awk -F== '/ATTR{address}/ {print $2}')
 
+  if [ "$INT_MAC" = "$EXT_MAC" ] ; then
+    echo "Error: MAC address for $INTERNAL_DEV is same as for $EXTERNAL_DEV" >&2
+    exit 1
+  fi
+
   cat > $TARGET/etc/udev/rules.d/70-persistent-net.rules << EOF
 ## Generated by Sipwise deployment script
 SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}==$INT_MAC, ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="$INTERNAL_DEV"