fix Ansible documentation linter violations

[displague]

Part of #26

~I don't know how to generate the linting output that was quoted in the original post. Ideally we will bake that linter into our CI.~ see https://github.com/equinix/ansible-collection-metal/pull/33#issuecomment-825393648

• [ ] return device_id: no sample (check everywhere) (#53 ?)
• [x] short_description: line 1 ends with a dot (must not)
• [x] return capacity: line 1 does not end with a dot (in return sections lines must end with a dot)
• [ ] no "notes" section, it should, at least, contain info about check_mode support, please put something like:

  notes:

  • Supports / Does not support C(check_mode).

• [x] opt user_data: line 1 does not end with a dot (pleas recheck all the options end with a dot).

[displague]

I've captured the commands (full process) and output from a linting pass at d9bd3eb using https://github.com/Andersson007/ansible_reviewer in this gist: https://gist.github.com/displague/9aacc3bb335c0f55650a26518770d23d