Add /var/log/containers mount

The /var/log/containers mount is necessary for use with fluentd.
The kubelet creates symlinks that grab the pod name, namespace,
and container name from this directory on the host, so it needs
to be mounted

Change-Id: Ib1e4769b739d1f85ab22ad66612fb96d4c917b33

tools/kubeadm-aio/assets/usr/bin/kubelet

@@ -45,6 +45,7 @@ else
         --volume=/var/lib/docker/:/var/lib/docker:rw \
         --volume=/var/lib/kubelet/:/var/lib/kubelet:rshared \
         --volume=/var/run:/var/run:rw \
+        --volume=/var/log/containers:/var/log/containers:rw \
         --volume=/etc/kubernetes:/etc/kubernetes:rw \
         --volume=/etc/hosts:/etc/hosts:rw \
         --volume=/etc/resolv.conf:/etc/resolv.conf:rw \