Add etcd-events cluster for kube-apiserver

Now adding unjoined members to existing etcd cluster
occurs one at a time so that the cluster does not
lose quorum.

- Run docker run from script rather than directly from systemd target
- Refactoring styling/templates

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

Closes: #1073
Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

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.

* Drop linux capabilities for unprivileged containerized
  worlkoads Kargo configures for deployments.
* Configure required securityContext/user/group/groups for kube
  components' static manifests, etcd, calico-rr and k8s apps,
  like dnsmasq daemonset.
* Rework cloud-init (etcd) users creation for CoreOS.
* Fix nologin paths, adjust defaults for addusers role and ensure
  supplementary groups membership added for users.
* Add netplug user for network plugins (yet unused by privileged
  networking containers though).
* Grant the kube and netplug users read access for etcd certs via
  the etcd certs group.
* Grant group read access to kube certs via the kube cert group.
* Remove priveleged mode for calico-rr and run it under its uid/gid
  and supplementary etcd_cert group.
* Adjust docs.
* Align cpu/memory limits and dropped caps with added rkt support
  for control plane.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

* 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>

Creating the unit using default settings early on
and then changing it during network_plugin section
leads to too many docker restarts and duplicated code.

Reversed Wants= dependence on docker.service so it does not
restart docker when reloading systemd

Consolidated all docker restart handlers.

* 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>

Changed Wants=docker.service to docker.socket

Renamed handlers for reloading systemd to contain role in task name.

Improved docker reload command to wait for etcd to be
up before proceeding. Switched reload to run restart
because it can't reload if it is not guaranteed to be
in running state.

* Enforce a etcd-proxy role to a k8s-cluster group members. This
provides an HA layout for all of the k8s cluster internal clients.
* Proxies to be run on each node in the group as a separate etcd
instances with a readwrite proxy mode and listen the given endpoint,
which is either the access_ip:2379 or the localhost:2379.
* A notion for the 'kube_etcd_multiaccess' is: ignore endpoints and
loadbalancers and use the etcd members IPs as a comma-separated
list. Otherwise, clients shall use the local endpoint provided by a
etcd-proxy instances on each etcd node. A Netwroking plugins always
use that access mode.
* Fix apiserver's etcd servers args to use the etcd_access_endpoint.
* Fix networking plugins flannel/calico to use the etcd_endpoint.
* Fix name env var for non masters to be set as well.
* Fix etcd_client_url was not used anywhere and other etcd_* facts
evaluation was duplicated in a few places.
* Define proxy modes only in the env file, if not a master. Del
an automatic proxy mode decisions for etcd nodes in init/unit scripts.
* Use Wants= instead of Requires= as "This is the recommended way to
hook start-up of one unit to the start-up of another unit"
* Make apiserver/calico Wants= etcd-proxy to keep it always up

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Co-authored-by: Matthew Mosesohn <mmosesohn@mirantis.com>

Running etcd in Docker reduces the number of individual file
downloads and services running on the host.

Note: etcd container v3.0.1 moves bindir to /usr/local/bin

Fixes: #298