Fix/ubuntu xenial resolv conf

[AtzeDeVries]

a PR to fix #3334

[Atoms]

ci check this

[Atoms]

/lgtm
/approve

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[KouriR]

Ideally this should check if /run/systemd/resolve/resolv.conf exists first. If not, it should keep using /etc/resolv.conf.

[woopstar]

you should be able to set the kube_resolv_conf in group vars

[KouriR]

A role var can't be overridden by group vars. I can use extra vars but that's not ideal for me.
P.S. nice avatar

[kowalskey]

I also concur that this should be configurable. We run ubuntu 18.04 without systemd-resolved and stubled upon inability to override kube_resolv_conf