When it initially landed in kubernetes/kubernetes@c6e9ad066e (Initial
node drain implementation for #3885, 2015-08-30,
kubernetes/kubernetes#16698), the drain logic looked in a created-by
annotation for recognized kinds [1], so listing the set of recognized
kinds was a clear approach.
Sometime later, the source moved into ownerReferences, but the
hard-coded set of recognized controller kinds remained.
When kubernetes/kubernetes@2f1108451f (Remove hard-coded
pod-controller check, 2017-12-05, kubernetes/kubernetes#56864) removed
the hard-coded set of recognized controller kinds, it should have also
updated these messages to remove stale references to the previous
hard-coded values. This commit catches the message strings up with
that commit.
[1]: c6e9ad066e (diff-211259b8a8ec42f105264c10897dad48029badb538684e60e43eaead68c3d219R216)
Kubernetes-commit: 587f4f04cc5fc18f4e85ed6a4a06bbf1bfee0496