Enable custom bond mode

templates/interfaces.j2

@@ -95,7 +95,11 @@ auto {{ item['name'] }}
 {% if item['mtu'] is defined %}
 	mtu {{ item['mtu'] }}
 {% endif %}
-	bond-mode active-backup
+{% if item['bond-mode'] is defined %}
+	bond-mode {{ item['bond-mode'] }}
+{% else %}
+	bond-mode active-backup	
+{% endif %}
 	bond-miimon 100
 	bond-slaves none
 {% if item['routes'] is defined %}