"shell" step doesn't support check mode, which currently leads to failures,
when Ansible is being run in check mode (because Ansible doesn't run command,
assuming that command might have effect, and no "rc" or "output" is registered).

Setting "check_mode: no" allows to run those "shell" commands in check mode
(which is safe, because those shell commands doesn't have side effects).

- Exclude kubelet CPU/RAM (kube-reserved) from cgroup. It decreases a
  chance of overcommitment
- Add a possibility to modify Kubelet node-status-update-frequency
- Add a posibility to configure node-monitor-grace-period,
  node-monitor-period, pod-eviction-timeout for Kubernetes controller
  manager
- Add Kubernetes Relaibility Documentation with recomendations for
  various scenarios.

Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

Raise readiness probe initial time to 60 (was 30)

Update code and docs for that assumption.

kubelet lost the ability to load kernel modules.  This
puts that back by adding the lib/modules mount to kubelet.

The new variable kubelet_load_modules can be set to true
to enable this item.  It is OFF by default.

- Since Weave 1.8.x was rewritten in Golang we may decrease RAM settings
  to continue using g1-small for CI

Daemonsets cannot be simply upgraded through a single API call,
regardless of any kubectl documentation. The resource must be
purged and then recreated in order to make any changes.

Also make no-resolv unconditional again. Otherwise, we may end up in
a resolver loop. The resolver loop was the cause for the piling up
parallel queries.

Faster gzip improves CI deploy times by at least 2 mins.

Fixes #982

Fixes upgrade from pre-individual node cert envs.

Reduce election timeout to 5000ms (was 10000ms)
Raise heartbeat interval to 250ms (was 100ms)
Remove etcd cpu share (was 300)
Make etcd_cpu_limit and etcd_memory_limit optional.

Netchecker is rewritten in Go lang with some new args instead of
env variables. Also netchecker-server no longer requires kubectl
container. Updating playbooks accordingly.

kube_apiserver_node_port_range should be accessible only
to kube-proxy and not be taken by a dynamic port allocation.

Potentially temporary if https://github.com/kubernetes/kubernetes/issues/40920
gets fixed.

- Remove weave CPU limits from .gitlab-ci.yml. Closes: #975
- Fix weave version in documentation

Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

'absible_ssh_host' is deprecated in Ansible 2.0 and at least
'contrib/inventory_builder/inventory.py' uses 'ansible_host' instead.

- Docker 1.12 and further don't need nsenter hack. This patch removes
  it.  Also, it bumps the minimal version to 1.12.

Closes #776

Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

- Set recommended CPU settings
- Cleans up upgrade to weave 1.82. The original WeaveWorks
daemonset definition uses weave-net name.
- Limit DS creation to master
- Combined 2 tasks into one with better condition

if the system doesn't have any config files at all.

Cleans up upgrade to weave 1.82. The original WeaveWorks
daemonset definition uses weave-net name.

Use stdin instead of bash args to pass node filenames and base64 data.
Use tempfile for master cert data

When DNSMasq is configured to read its settings
from a folder ('-7' or '--conf-dir' option) it only
checks that the directory exists and doesn't fail if
it's empty. It could lead to a situation when DNSMasq
is running and handles requests, but not properly
configured, so some of queries can't be resolved.

For consistancy with kubernetes services we should use the same
hostname for nodes, which is 'ansible_hostname'.

Also fixing missed 'kube-node' in templates, Calico is installed
on 'k8s-cluster' roles, not only 'kube-node'.