Removed unnecessary root user

  * using separated vault roles for generate certs with different `O` (Organization) subject field;
  * configure vault roles for issuing certificates with different `CN` (Common name) subject field;
  * set `CN` and `O` to `kubernetes` and `etcd` certificates;
  * vault/defaults vars definition was simplified;
  * vault dirs variables defined in kubernetes-defaults foles for using
  shared tasks in etcd and kubernetes/secrets roles;
  * upgrade vault to 0.8.1;
  * generate random vault user password for each role by default;
  * fix `serial` file name for vault certs;
  * move vault auth request to issue_cert tasks;
  * enable `RBAC` in vault CI;

* Adding yaml linter to ci check

* Minor linting fixes from yamllint

* Changing CI to install python pkgs from requirements.txt

- adding in a secondary requirements.txt for tests
- moving yamllint to tests requirements

Closes: #1135
Closes: #1026
Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

Operator can specify any port for kube-api (6443 default) This helps in
case where some pods such as Ingress require 443 exclusively.

Closes: 820
Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

* Leave all.yml to keep only optional vars
* Store groups' specific vars by existing group names
* Fix optional vars casted as mandatory (add default())
* Fix missing defaults for an optional IP var
* Relink group_vars for terraform to reflect changes

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