Broken unit tests exposed by Python 3.12+

[vicaya]

The 2 test_init_successful_connection tests in backend/app/tests/scripts/test_\*_pre_start.py are basically noops, due to misuses of MagicMock(return_value=True). The 2 unit tests would error out due to unknown attributes (called_once_with) when running bash scripts/test.sh under python 3.12+, which tightened up the MagicMock implementation.

PR would follow.