Fix race conditions in tests for parallelized testing

[mferrera]

Currently we cannot reliably use pytest-xdist to parallelize tests because there appear to be race conditions

FAILED tests/test_units/test_dataio.py::test_norwegian_letters_globalconfig_as_json - FileNotFoundError: [Errno 2] No such file or directory: '/private/var/folders/9_/94pcly3n7x7f29...
FAILED tests/test_units/test_objectdataprovider_class.py::test_regsurf_preprocessed_observation - FileNotFoundError: [Errno 2] No such file or directory: '/private/var/folders/9_/94pcly3n7x7f29...
FAILED tests/test_units/test_preprocessed.py::test_export_preprocessed_surfacefile - FileNotFoundError: [Errno 2] No such file or directory: '/private/var/folders/9_/94pcly3n7x7f29...
FAILED tests/test_units/test_preprocessed.py::test_export_to_results_folder - FileNotFoundError: [Errno 2] No such file or directory: '/private/var/folders/9_/94pcly3n7x7f29...
FAILED tests/test_units/test_rms_context.py::test_regsurf_export_file_set_name - FileNotFoundError: [Errno 2] No such file or directory: '/private/var/folders/9_/94pcly3n7x7f29...
FAILED tests/test_units/test_rms_context.py::test_grid_export_file_set_name - FileNotFoundError: [Errno 2] No such file or directory: '/private/var/folders/9_/94pcly3n7x7f29...