Bump DO-Kubernetes to v1.16

[mjuric]

Once jupyterhub/zero-to-jupyterhub-k8s#1444 is resolved, bump the allowed k8s version to 1.16.

[consideRatio]

ping @mjuric - It works on k8s 1.16 now according to our CI system, but so far untested in the real world. I'd appreciate some feedback if you try it, my environment is on k8s 1.14

[mjuric]

@consideRatio Thanks!

Confirming it worked on Digital Ocean's k8s v1.16, with one glitch -- the progress updates while a user's pod is starting seems to be gone. Instead, I get repeated 'Server requested' messages:

until the pod finally launches and I'm redirected to /tree.

Regression in kubespawner, or a known issue?

Using jupyterhub/k8s-hub:0.9.0-alpha.1.058.002ae04 for the hub (default in the 0.9.0-alpha.1.060.6698eb9 helm chart).

[mjuric]

I can confirm the same "Server requested"... issue appears on k8s 1.15, when using the 0.9.0-alpha.1.060.6698eb9 version of the helm chart. Rolling back to 0.9.0-alpha.1.028.00bc15c chart restores the normal behavior.

[consideRatio]

Any logs from the hub pod about issues from the spawner?