Return back --network-plugin=cni (#883)

pkg/userdata/centos/testdata/kubelet-v1.17-aws-external.yaml

pkg/userdata/centos/testdata/kubelet-v1.17-aws.yaml

...erdata/centos/testdata/kubelet-v1.17-vsphere-mirrors.yaml

...userdata/centos/testdata/kubelet-v1.17-vsphere-proxy.yaml

pkg/userdata/centos/testdata/kubelet-v1.17-vsphere.yaml

pkg/userdata/centos/testdata/kubelet-v1.18-aws.yaml

pkg/userdata/centos/testdata/kubelet-v1.19-aws.yaml

pkg/userdata/centos/testdata/kubelet-v1.20-aws.yaml

pkg/userdata/coreos/testdata/v1.17.16-vsphere.yaml

...s/testdata/v1.18.14-aws-disable-auto-update-external.yaml

...ata/coreos/testdata/v1.18.14-aws-disable-auto-update.yaml

...rdata/coreos/testdata/v1.18.14-aws-disable-locksmith.yaml

...a/coreos/testdata/v1.18.14-aws-disable-update-engine.yaml

...18.14-openstack-auto-update-kubelet-v-version-prefix.yaml

...testdata/v1.18.14-openstack-auto-update-multiple-dns.yaml

pkg/userdata/coreos/testdata/v1.18.14-vsphere-mirrors.yaml

...reos/testdata/v1.18.14-vsphere-overwrite-cloudconfig.yaml

pkg/userdata/coreos/testdata/v1.18.14-vsphere-proxy.yaml

...ata/coreos/testdata/v1.18.14-vsphere-static-ipconfig.yaml

pkg/userdata/coreos/testdata/v1.18.14-vsphere.yaml