Previously we used to do an idempotent sync all active VIPs any time we
got a service or endpoint update. However, this only worked when we
assumed a single-stack deployment model where IPs were never deleted
unless the whole service was deleted.
In a dual-stack model, we can add / remove LoadBalancer IPs and Cluster
IPs on updates. Given this, we need to take into account the finite
change that happens, and not just revert to sync-all because we'll never
stop advertising IPs that should be removed.
As a fall-back, we still have the outer Run loop that syncs all active
routes every X amount of seconds (configured by user CLI parameter). So
on that timer we'll still have something that syncs all active VIPs and
works as an outer control loop to ensure that desired state eventually
becomes active state if we accidentally remove a VIP that should have
been there.
