Add an extra network node for HA

Given keepalived runs on the network node, we should have a minimum of
two by default for high availability.

Change-Id: Ifbd68e456dc93319df8e85017fd9f4db09f05929

ansible/inventory/multinode

@@ -13,6 +13,7 @@ control03
 # This can be the same as a host in the control group
 [network]
 network01
+network02
 
 [compute]
 compute01

releasenotes/notes/add-extra-network-node-4b6e4e2663950b9c.yaml

+---
+upgrade:
+  - The default multinode inventory now specifies a
+    second network node for high availability of the
+    VIP.