fix: fix `CentOS Linux-7` and add `os` details from current CI setup

[myii]

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
• [x] [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

• [x] [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

Realised that there was an erroneous entry in osfingermap.yaml here:

• https://github.com/saltstack-formulas/openldap-formula/pull/24#discussion_r371062614

Added the rest of the OS details from our current supported CI platforms, to prevent having to look up the values each time from elsewhere.

Pillar / config required to test the proposed changes

As-is.

Debug log showing how the proposed changes work

N/a.

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

[myii]

@baby-gnu @aboe76 Thanks for the reviews.

[saltstack-formulas-travis]

:tada: This PR is included in version 4.0.3 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: