Rework systemd service units

* Add for docker system units:
    ExecReload=/bin/kill -s HUP $MAINPID
    Delegate=yes
    KillMode=process.
* Add missed DOCKER_OPTIONS for calico/weave docker systemd unit.
* Change Requires= to a less strict and non-faily Wants=, add missing
  Wants= for After=.
* Align wants/after in a wat if Wants=foo, After= has foo as well.
* Make wants/after docker.service to ask for the docker.socket as well.
* Move "docker rm -f" commands from ExecStartPre= to ExecStopPost=.
  hooks to ensure non-destructive start attempts issued by Wants=.

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

roles/network_plugin/flannel/templates/systemd-docker.service

@@ -2,22 +2,26 @@
 Description=Docker Application Container Engine
 Documentation=http://docs.docker.com
 {% if ansible_os_family == "RedHat" %}
-After=network.target
+After=network.target docker-storage-setup.service
 Wants=docker-storage-setup.service
 {% elif ansible_os_family == "Debian" %}
 After=network.target docker.socket
-Requires=docker.socket
+Wants=docker.socket
 {% endif %}
 
 [Service]
 Type=notify
 EnvironmentFile=-/etc/default/docker
 Environment=GOTRACEBACK=crash
+ExecReload=/bin/kill -s HUP $MAINPID
+Delegate=yes
+KillMode=process
 ExecStart=/usr/bin/docker daemon \
           $OPTIONS \
           $DOCKER_STORAGE_OPTIONS \
           $DOCKER_NETWORK_OPTIONS \
-          $INSECURE_REGISTRY
+          $INSECURE_REGISTRY \
+          $DOCKER_OPTS
 LimitNOFILE=1048576
 LimitNPROC=1048576
 LimitCORE=infinity