Curl is more ubiquitous than wget. For instance, the GCE centos-7 and
rhel-7 image families ship curl by default, but not wget.
Looking at the shell scripts under cluster/, they tend to use curl more
than wget. (The ones that use wget, such as get-kube.sh, try curl first
and only fallback to wget if it's not available.)
Tested: by running node-e2e-test on Ubuntu, COS and CentOS.
This adds a simple CNI configuration which is added to the node during test setup.
This also modifies the default flags in services/kubelet.go to specify the "cni-bin-dir"
and the "cni-conf-dir" and removes the "network-plugin-dir" flag. This leaves the default
network plugin to kubenet.