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>

roles/etcd/tasks/pre_upgrade.yml

@@ -1,3 +1,4 @@
+---
 - name: "Pre-upgrade | check for etcd-proxy unit file"
   stat:
     path: /etc/systemd/system/etcd-proxy.service
@@ -49,3 +50,7 @@
     awk -F"[: =]" '{print "{{ bin_dir }}/etcdctl --peers={{ etcd_access_addresses | regex_replace('https','http') }} member update "$1" https:"$7":"$8}' | bash
   run_once: true
   when: 'etcd_member_list.rc == 0 and "http://" in etcd_member_list.stdout'
+
+- name: "Pre-upgrade | share access to etcd certs for its users"
+  shell: chmod g+r {{ etcd_cert_dir }}/*.pem
+  failed_when: false