MAR-192: Switch to using NTPsec NTP server for increased security:

- This has for some time been a way better option, and it should also
provide for compatibility with Debian 12 Bookworm.

MAR-154: Drop support for Python 2.7 from the common role:

- This primarily concerns removal of pip requirements upgrade checks
for Python 2.7.
- The old Python 3-specific paths are getting deprecated, and the
Python 2 paths will be used instead.
- Set permissions on pipreqcheck directory explicitly (because of
deprecation testing).

MAR-182: Added ability to specify input requirements for running pip package upgrade checks against helper virtual environments:

- These environments are used for running the package upgrade checks
themselves.

MAR-149: Minor syntax fixes for Python 3 in tests for common role:

- Do not use the unicode function (this still might break, need to
test it).
- Fix syntax used for catching exceptions within variables.
- Fix one small linting error related to row length.

MAR-149: Switch to using File.content_string instead of File.content in tests for all roles:

- The .content variant returns contents as bytes, while the
content_string returns a string (which is what is wanted in
practically all cases).

MAR-148: Clean-up TODO entries for the common role coming from bugs in earlier versions of software:

- Switch to using the systemd task for reloads.
- Add back validation of pipreqcheck activation script file
permissions.
- Add back validation of missing ntp/ntpdate packages.

MAR-129: Updated backup_server role tests:

- Move the 'ss' utility out of place in order to be able to test if
sockets are
open (seehttps://github.com/philpep/testinfra/pull/320).
- Updated tests to use correct mechanism for setting-up list of
machines where the tests should be run.

MAR-128: Upgraded tests for common role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (easies
idempotence tests).
- Updated tests to reference the yml inventory file.
- Updated tests to use new fixture (host instead of individual ones).
- Switched to extracting IP address instead of hard-coding it in a
couple of tests.
- Fixed invalid indentation on task responsible for creating the
pipreqcheck Python virtual environment.