[keepalived-vip] Should allow for multiple NICs

[shift]

The current implementation doesn't have support for multiple network interfaces. It's more of a first one wins.

A better implementation would be to use labels on the nodes to signify which is the internal and which is the external interfaces.

The internal interface is the one which the VRRP keepalive/heartbeat is used for.
The external interface is the one which the VIP is assigned too.

I'm currently swaying towards using a labels like contrib.kubernetes.io/keepalived-vip/internal and contrib.kubernetes.io/keepalived-vip/external. And if present to not bother with the current interface code and instead to use those values in the keepalived.conf generated.

Even with RBAC enabled the default example policy allows access to the nodes resource, so no other changes should be required on the deployment side of things.