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/etcd/tasks/pre_upgrade.yml

@@ -26,12 +26,12 @@
     - /etc/init.d/etcd-proxy
 
 - name: "Pre-upgrade | find etcd-proxy container"
-  command: docker ps -aq --filter "name=etcd-proxy*"
+  command: "{{ docker_bin_dir }}/docker ps -aq --filter 'name=etcd-proxy*'"
   register: etcd_proxy_container
   failed_when: false
 
 - name: "Pre-upgrade | remove etcd-proxy if it exists"
-  command: "docker rm -f {{item}}"
+  command: "{{ docker_bin_dir }}/docker rm -f {{item}}"
   with_items: "{{etcd_proxy_container.stdout_lines}}"
 
 - name: "Pre-upgrade | check if member list is non-SSL"