Remove nsenter workaround

- 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>

roles/kubernetes/secrets/tasks/gen_certs.yml

@@ -160,6 +160,20 @@
       {%- endif %}
   tags: facts
 
+- name: SSL CA directories | Set SSL CA directories
+  set_fact:
+    ssl_ca_dirs: "[
+      {% if ansible_os_family in ['CoreOS', 'Container Linux by CoreOS'] -%}
+      '/usr/share/ca-certificates',
+      {% elif ansible_os_family == 'RedHat' -%}
+      '/etc/pki/tls',
+      '/etc/pki/ca-trust',
+      {% elif ansible_os_family == 'Debian' -%}
+      '/usr/share/ca-certificates',
+      {% endif -%}
+    ]"
+  tags: facts
+
 - name: Gen_certs | add CA to trusted CA dir
   copy:
     src: "{{ kube_cert_dir }}/ca.pem"