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/network_plugin/calico/rr/tasks/main.yml

@@ -12,8 +12,8 @@
     dest: "{{ calico_cert_dir }}"
     state: directory
     mode: 0750
-    owner: root
-    group: root
+    owner: "{{ netplug_user }}"
+    group: "{{ netplug_group }}"
 
 - name: Calico-rr | Link etcd certificates for calico-node
   file:
@@ -31,8 +31,8 @@
     path: /var/log/calico-rr
     state: directory
     mode: 0755
-    owner: root
-    group: root
+    owner: "{{ netplug_user }}"
+    group: "{{ netplug_group }}"
 
 - name: Calico-rr | Write calico-rr.env for systemd init file
   template: src=calico-rr.env.j2 dest=/etc/calico/calico-rr.env

roles/network_plugin/calico/rr/templates/calico-rr.service.j2

@@ -6,7 +6,7 @@ Requires=docker.service
 [Service]
 EnvironmentFile=/etc/calico/calico-rr.env
 ExecStartPre=-{{ docker_bin_dir }}/docker rm -f calico-rr
-ExecStart={{ docker_bin_dir }}/docker run --net=host --privileged \
+ExecStart={{ docker_bin_dir }}/docker run --net=host \
  --name=calico-rr \
  -e IP=${IP} \
  -e IP6=${IP6} \
@@ -16,6 +16,10 @@ ExecStart={{ docker_bin_dir }}/docker run --net=host --privileged \
  -e ETCD_KEY_FILE=${ETCD_KEY_FILE} \
  -v /var/log/calico-rr:/var/log/calico \
  -v {{ calico_cert_dir }}:{{ calico_cert_dir }}:ro \
+{% for c in calico_drop_cap %}
+ --cap-drop={{ c }} \
+{% endfor %}
+ -u {{ netplug_user_id }}:{{ netplug_group_id }} --group-add {{ etcd_cert_group }} \
  --memory={{ calico_rr_memory_limit|regex_replace('Mi', 'M') }} --cpu-shares={{ calico_rr_cpu_limit|regex_replace('m', '') }} \
  {{ calico_rr_image_repo }}:{{ calico_rr_image_tag }}