Update to golang 1.12.9

[justinsb]

We particularly want the http fixes in 1.12.8:

https://golang.org/doc/devel/release.html#go1.12.minor

[k8s-ci-robot]

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[zetaab]

/test pull-kops-e2e-kubernetes-aws

[zetaab]

/lgtm

[rifelpet]

It looks like protokube is having docker issues now:

Aug 31 07:48:47.726791 ip-172-20-51-72 systemd[1]: Started Kubernetes Protokube Service.
Aug 31 07:48:47.789728 ip-172-20-51-72 docker[2661]: /usr/bin/docker: invalid reference format.
Aug 31 07:48:47.789728 ip-172-20-51-72 docker[2661]: See '/usr/bin/docker run --help'.
Aug 31 07:48:47.791584 ip-172-20-51-72 systemd[1]: protokube.service: Main process exited, code=exited, status=125/n/a
Aug 31 07:48:47.792388 ip-172-20-51-72 systemd[1]: protokube.service: Unit entered failed state.
Aug 31 07:48:47.792433 ip-172-20-51-72 systemd[1]: protokube.service: Failed with result 'exit-code'.
Aug 31 07:48:49.972783 ip-172-20-51-72 systemd[1]: protokube.service: Service hold-off time over, scheduling restart.
Aug 31 07:48:49.973059 ip-172-20-51-72 systemd[1]: Stopped Kubernetes Protokube Service.

[rifelpet]

/lgtm