Adding Network MTU parameter to VLANs

Change-Id: Id0aefc4a8ee8e07ec74ef4a519d646e9fc0120ec
diff --git a/README.rst b/README.rst
index 4cc62bd..ea7c7d6 100644
--- a/README.rst
+++ b/README.rst
@@ -59,6 +59,7 @@
             0:
               name: 'vlan 0'
               description: Deploy VLAN
+              mtu: 1500
               dhcp: true
               # FIXME: after refactoring domain module, it should be
               # fixed exactly for FQDN, not only 'hostname'