Fix dhcp multiple default gateways issue

The system only adds one gateway and if it receives default gateway from
incorrect interface (like control plane primary interface), the instance loses
access to external network.

Fixing by making primary interfaces (control plane) static.

Change-Id: I511f6721c2ecac29eccbdd63160f748c1cc2ee07
diff --git a/classes/cluster/virtual-mcp11-contrail/stacklight/server.yml b/classes/cluster/virtual-mcp11-contrail/stacklight/server.yml
index 9345cca..00f12ca 100755
--- a/classes/cluster/virtual-mcp11-contrail/stacklight/server.yml
+++ b/classes/cluster/virtual-mcp11-contrail/stacklight/server.yml
@@ -42,4 +42,6 @@
         ens4:
           enabled: true
           type: eth
-          proto: dhcp
+          proto: static
+          address: ${_param:single_address}
+          netmask: 255.255.255.0