[kubernetes/kubernetes] Release v1.15.11 - v1.15.11

CRANK

See [kubernetes-announce@](https://groups.google.com/forum/#!forum/kubernetes-announce) and [CHANGELOG/CHANGELOG-1.15.md](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.15.md#v11511) for details. SHA256 for `kubernetes.tar.gz`: `911aab8413b5a700593a4f050b5ff24f1e2cb6cf412f106011e0f5b738433b02` SHA512 for `kubernetes.tar.gz`: `7834a01bf5e4cc5d93791f0dce512ff8f40c92e588c980567fb6d715bb707a650511495d323cd27e5e8f524577efb04adb07478ecbe55876f32c7f1cc055e907` Additional binary downloads are linked in the [CHANGELOG/CHANGELOG-1.15.md](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.15.md#downloads-for-v11511).