MAR-243: Drop inventory_hostname use from tests where possible:

- Primarily focused on Ansible playbooks and variable files.
- The variable is still used within some Python test fixtures. Test
behaviour should still be correct, with one advantage being that
lookups should be much faster than using the setup module (which
would require running Ansible code on each remote/test machine).

MAR-236: Add auxiliary object class to LDAP directory for optional countryName and friendlyCountryName attributes:

- Makes it easier to specify free-form optional country name in
LDAP-backed address books.
- Object class uses Majic-specific PEN (Private Enterprise Number)
"namespace" - 1.3.6.1.4.1.40926.417.2.1 (40926 is Majic PEN, 417
stands for LDAP, 2 stands for object class, and 1 is incremental
sequence number). The 417 is result of adding together lower-cased
letters LDAP in their decimal value.

MAR-230: Add support for TLSv1.3 to the ldap_server role and drop TLSv1.1 from tests:

- Update the role defaults, make sure to include additional priority
strings for TLSv1.3.
- Document the specifics of TLSv1.3 cipher configuration.
- Update tests.

MAR-150: Use fixtures for X.509 artefacts in the ldap_server role:

- Removed the statically generated artefacts.
- Generate X.509 artefacts for tests using Gimmecert.
- Updated paths to point to generated artefacts.
- Introduced cleanup playbook for removing generated artefacts.

MAR-162: Deduplicate TLS private key/certificate tests for LDAP server role:

- Rename the key/certificate files to match the Ansible inventory
name.
- Move the tests into test_default.py.
- Change the key/certificate extensions to be more descriptie.

MAR-129: Updated ldap_server role for new Molecule and Ansible:

- Fixed syntax warnings.
- Moved test playbook variables into group_vars.
- Optimised the invocation of test playbook.
- Remove the 'ss' utility from test machines in order to properly test
the unix sockets.
- Fixed how the hosts are being referenced in tests.