azure-container-networking: CNI/IPAM plugin on Ubuntu 17.10 breaks DNS

Is this a request for help?:

yes

Is this an ISSUE or FEATURE REQUEST? (choose one):

ISSUE

Which release version?:

v1.0.3

Which componenet (CNI/IPAM/CNM/CNS):

CNI/IPAM

Which Orchestrator and version (e.g. Kubernetes, Docker) Kubernetes

What happened: Activating the CNI plugin on Ubuntu 17.10 breaks name resolution (DNS). The switch from eth0 to azure0 leaves DNS in an unusable state.

What you expected to happen: DNS should continue to work

How to reproduce it (as minimally and precisely as possible):

1. Provision a Kubernetes cluster with an Ubuntu 17.10 node and CNI/IPAM configured
2. Schedule a pod
3. Pod starts to run and errors with ErrImagePull due to being unable to resolve docker.io to pull images

At this point, the node must be rebooted for DNS to work again.

Anything else we need to know: Ubuntu 17.10 uses systemd-resolved as a caching, stub nameserver. More info here: http://manpages.ubuntu.com/manpages/xenial/man8/systemd-resolved.service.8.html

cc @lachie83