The etcd3 storage now attempts to fill partial pages to prevent clients
having to make more round trips (latency from server to etcd is lower
than client to server). The server makes repeated requests to etcd of
the current page size, then uses the filter function to eliminate any
matches. After this change the apiserver will always return full pages,
but we leave the language in place that clients must tolerate it.

Reduces tail latency of large filtered lists, such as viewing pods
assigned to a node.