MAR-129: Updated LDAP client role and its tests for new Molecule and Ansible:

- Fixed linting issues.
- Moved test playbook variables into group_vars.
- Include linting configuration for tests from top-level directory.
- Updated how the target hosts are refenced in tests.
- Fixed Ansible warnings.

MAR-128: Upgraded tests for ROLE_NAME role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (eases
idempotence tests).
- Updated tests to reference the yml inventory file.
- Updated tests to use new fixture (host instead of individual ones).