perf(users/init.sls): dedup groups and directories creation

[stasjok]

PR progress checklist (to be filled in by reviewers)

• Changes to documentation are appropriate (or tick if not required)
• Changes to tests are appropriate (or tick if not required)
• Reviews completed

---

What type of PR is this?

Primary type

• [build] Changes related to the build system
• [chore] Changes to the build process or auxiliary tools and libraries such as documentation generation
• [ci] Changes to the continuous integration configuration
• [feat] A new feature
• [fix] A bug fix
• [perf] A code change that improves performance
• [refactor] A code change that neither fixes a bug nor adds a feature
• [revert] A change used to revert a previous commit
• [style] Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)

Secondary type

• [docs] Documentation changes
• [test] Adding missing or correcting existing tests

Does this PR introduce a BREAKING CHANGE?

No.

Related issues and/or pull requests

Describe the changes you're proposing

• don't create required directories multiple times, e.g. if we create many users
  with default home directories, there won't be multiple file.directory states to create /home
• don't create / directory, e.g. for /root home directory
• don't create groups multiple times, e.g. if many users share the same group (even for prime groups like users)

Pillar / config required to test the proposed changes

groups:
  sudo_adm:
    system: yes

users:
  root:
    password: '!'
    user_dir_mode: 700
    ssh_auth_file: some_key
  test1:
    groups:
      - sudo_adm
      - test_group1
  test2:
    groups:
      - sudo_adm
      - test_group1
      - test_group2
  test3:
    home: /tmp/some/random/homedir
    prime_group:
      name: users
    groups:
      - test_group2
  test4:
    createhome: no
    prime_group:
      name: users

Debug log showing how the proposed changes work

Documentation checklist

• Updated the README (e.g. Available states).
• Updated pillar.example.

Testing checklist

• Included in Kitchen (i.e. under state_top).
• Covered by new/existing tests (e.g. InSpec, Serverspec, etc.).
• Updated the relevant test pillar.

Additional context