[tests/python] Remove unnecessary call to rospack

tests/python/test_com_estimation.py

tests/python/test_dcm_controller_talos.py

tests/python/test_dcm_distribute.py

tests/python/test_dcm_estimator.py

tests/python/test_distribute.py

tests/python/test_dummy_wpgen.py

tests/python/test_round_double_to_int.py

tests/python/test_simple_distribute.py

tests/python/test_state_transformation.py