github.com/hashicorp/golang-lru is MPL 2 licensed, which means that
anyone who distributes code or binaries that incorporates it needs to
include its source code, even if they haven't made any modifications.
Since lrucacheexpire is picked up as a dependency of using the shared
informers in client-go, that's potentially a lot of distributors.
Most other deps of client-go are Apache 2.0, MIT, or BSD-like
licensed, which only requires including the license.
Rather than reverting to groupcache/lru, I just reimplemented the
functionality we need, which isn't much.
Kubernetes-commit: ecc53182475a00a4a1dc8ca1e056b0deb6bd430c
