Systemd units, limits, and bin path fixes

* Add restart for weave service unit
* Reuse docker_bin_dir everythere
* Limit systemd managed docker containers by CPU/RAM. Do not configure native
  systemd limits due to the lack of consensus in the kernel community
  requires out-of-tree kernel patches.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/kubernetes/node/templates/kubelet-container.j2

@@ -1,5 +1,5 @@
 #!/bin/bash
-/usr/bin/docker run --privileged \
+{{ docker_bin_dir }}/docker run --privileged \
 --net=host --pid=host --name=kubelet --restart=on-failure:5 \
 -v /etc/cni:/etc/cni:ro \
 -v /opt/cni:/opt/cni:ro \
@@ -9,6 +9,7 @@
 -v {{ docker_daemon_graph }}:/var/lib/docker \
 -v /var/run:/var/run \
 -v /var/lib/kubelet:/var/lib/kubelet \
+--memory={{ kubelet_memory_limit|regex_replace('Mi', 'M') }} --cpu-shares={{ kubelet_cpu_limit|regex_replace('m', '')  }} \
 {{ hyperkube_image_repo }}:{{ hyperkube_image_tag}} \
 nsenter --target=1 --mount --wd=. -- \
 ./hyperkube kubelet \