[edge] testing/kubelet: Failed to locate cni-plugins binaries

Context

kubelet daemon could not find cni-plugins binaries

Steps to reproduce

$ apk info kubelet # edge package
kubelet-1.18.4-r1 description:
Kubernetes - kubelet

$ rc-service kubelet start
$ ps aux | grep kubelet

12082 root      0:00 supervise-daemon kubelet --start --stdout /var/log/kubelet/kubelet.log --stderr /var/log/kubelet/kubelet.log /usr/bin/kubelet -- --cni-bin-dir=/usr/share/cni-plugins/bin --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --cgroup-driver=cgroupfs --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.2

12083 root      0:12 /usr/bin/kubelet --cni-bin-dir=/usr/share/cni-plugins/bin --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --cgroup-driver=cgroupfs --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.2

As you could see in the output above the --cni-bin-dir=/usr/share/cni-plugins/bin flag is declared for kubelet deamon, it means that kubelet would try to look into the /usr/share/cni-plugins/bin for cni-plugin binaries.

Because cni-plugins install binaries to /usr/libexec/cni/, kubelet would fail to locate cni-plugins binaries. The output of kubelet daemon clearly supports this:

$ cat /var/log/kubelet/kubelet.log
..
: [failed to find plugin "bridge" in path [/usr/share/cni-plugins/bin] failed to find plugin "portmap" in path [/usr/share/cni-plugins/bin] failed to find plugin "bandwidth" in path [/usr/share/cni-plugins/bin]]

Discussion

Is there any reason why we place cni-plugins to /usr/libexec/cni instead of /usr/share/cni-plugins/bin? I could see from the 09dff09b by @ncopa that the decision was more of a convention of storing executables in /usr/libexec/. If that's the case, I guess we should update the --cni-bin-dir in kubelet confd too.