Drop linux capabilities and rework users/groups

* 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>

inventory/group_vars/all.yml

@@ -36,10 +36,19 @@ retry_stagger: 5
 # Directory where python binary is installed
 # ansible_python_interpreter: "/opt/bin/python"
 
-# This is the group that the cert creation scripts chgrp the
-# cert files to. Not really changable...
+# This is the users/groups to own files and groups that the cert creation
+# scripts chgrp the cert files to
+kubelet_user: kube
+kubelet_group: kube
 kube_cert_group: kube-cert
 
+netplug_user: netplug
+netplug_group: netplug
+
+etcd_user: etcd
+etcd_group: etcd
+etcd_cert_group: etcd-cert
+
 # Cluster Loglevel configuration
 kube_log_level: 2