* 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>

Also place in global vars and do not repeat the kube_*_config_dir
and kube_namespace vars for better code maintainability and UX.

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

* Don't push containers if not changed
* Do preinstall role only once and redistribute defaults to
  corresponding roles

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

Move version/repo vars to download role.
Add container to download params, which overrides url/source_url,
if enabled.
Fix networking plugins download depending on kube_network_plugin.

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

Shorten deployment time with:
- Remove redundand roles if duplicated by a dependency and vice versa
- When a member of k8s-cluster, always install docker as a dependency
  of the etcd role and drop the docker role from cluster.yaml.
- Drop etcd and node role dependencies from master role as they are
  covered by the node role in k8s-cluster group as well. Copy defaults
  for master from node role.
- Decouple master, node, secrets roles handlers and vars to be used w/o
  cross references.

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