MAR-161: Make the ldap_server_domain parameter in the ldap_server role mandatory:

- Updated the ldap_server role.
- Removed default value for the parameter.
- Updated tests.
- Updated role reference documentation.
- Updated release notes.
- Dropped the .local from the Molecule instance names.

MAR-158: Update default TLS ciphers configuration in the ldap_server role:

- Updated the default value for parameter ldap_tls_ciphers.
- Updated tests, making them explicitly test for enabled and disabled
ciphers
- Updated role reference documentation.

MAR-162: Make the ldap_server_tls_certificate ldap_server_tls_key parameters mandatory:

- Updated release notes.
- Updated role reference documentation.
- Updated usage instructions to cover set-up of CA hierarchy earlier on
in the process.

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.

MAR-128: Upgraded tests for ldap_server 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).
- Fixed some linting issues.
- Use localhost as backup client server name. This should make it
simpler in future to cover more platforms.
- Set-up the /etc/hosts for tests with correct entries (primarily
aliases towards localhost to make it less important what the
hostname is).
- Renamed private key/certificate files for parameters-mandatory
server since server got renamed as well.
- Updated IP addresses used for testing to make it easier to test new
platforms in the future.
- Use inventory_hostname-based parameterisation of tests where
appropriate. Currently hard-coded value for this because
host.ansible.get_variables() produces errors.