Ensure test coverage on run path creation

[oyvindeide]

Run path creation is partially performed in python, but we would like to replace the remaning parts with a new implementation. What remains in C is the parameter sampling and saving to storage, which happens in initRun.

Known tests: test_parameter_sample_types.py test_create_run_path.py

Edit: definition of done: reviewed test coverage to make sure we are ready to reimplement.