Upgrade Kubernetes dependencies to 1.17

[timoreimann]

Details:

• Add script and Makefile target to easily update Kubernetes dependencies.
• Update Kubernetes dependencies to 1.17.5.
• Adjust code to dependency refactorings.

[waynr]

🙈

[waynr]

I took your suggestion from slack the other day: https://github.com/digitalocean/digitalocean-cloud-controller-manager/blob/master/scripts/update-k8s.sh

So instead of the dependencies that are already listed in the go.mod file the script linked above curls the upstream kubernetes go.mod at the appropriate version. It also moves the k8s.io/kubernetes dependency outside the loop since of course the upstream go.mod doesn't list itself as a dependency the same way it lists its components as dependencies and we do still need a replace directive for it.

[timoreimann]

I did pull down the CCM version of that script but then failed by committing an old, local copy I still had. :)

Should be fixed now.