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/download/tasks/main.yml

@@ -79,7 +79,7 @@
 
 #NOTE(bogdando) this brings no docker-py deps for nodes
 - name: Download containers if pull is required or told to always pull
-  command: "/usr/bin/docker pull {{ pull_args }}"
+  command: "{{ docker_bin_dir }}/docker pull {{ pull_args }}"
   register: pull_task_result
   until: pull_task_result|success
   retries: 4
@@ -115,7 +115,7 @@
   tags: facts
 
 - name: Download | save container images
-  shell: docker save "{{ pull_args }}" | gzip -{{ download_compress }} > "{{ fname }}"
+  shell: "{{ docker_bin_dir }}/docker save {{ pull_args }} | gzip -{{ download_compress }} > {{ fname }}"
   delegate_to: "{{ download_delegate }}"
   register: saved
   run_once: true
@@ -145,6 +145,6 @@
   tags: [upload, upgrade]
 
 - name: Download | load container images
-  shell: docker load < "{{ fname }}"
+  shell: "{{ docker_bin_dir }}/docker load < {{ fname }}"
   when: (ansible_os_family != "CoreOS" and inventory_hostname != groups['kube-master'][0] or download_delegate == "localhost") and download_run_once|bool and download.enabled|bool and download.container|bool
   tags: [upload, upgrade]

roles/download/tasks/set_docker_image_facts.yml

@@ -8,7 +8,7 @@
       {%- if pull_by_digest|bool %}{{download.repo}}@sha256:{{download.sha256}}{%- else -%}{{download.repo}}:{{download.tag}}{%- endif -%}
 
 - name: Register docker images info
-  shell: "{% raw %}/usr/bin/docker images -q | xargs /usr/bin/docker inspect -f '{{.RepoTags}},{{.RepoDigests}}'{% endraw %}"
+  shell: "{{ docker_bin_dir }}/docker images -q | xargs {{ docker_bin_dir }}/docker inspect -f {% raw %}'{{.RepoTags}},{{.RepoDigests}}'{% endraw %}"
   register: docker_images_raw
   failed_when: false
   when: not download_always_pull|bool