use ControlVirtualInterface for keepalived VRRP

Change keepalived.keepalive_interface so that it uses the actual
ControlVirtualInterface (bridge) for VRRP rather than the bridged
interface (NeutronPublicInterface).

Fixes the issue which caused keepalived to bring up the VIP on
all control nodes.

Change-Id: Ifc484d6a6086d9872210aa576f21d326f60b7d35
Merge "use ControlVirtualInterface for keepalived VRRP"