Renamed test_case_generator to sample_case_generator

Renamed test_case_generator.py to sample_case_generator.py because the
test engine is detecting test_case_generator.py as a test file.
Created test for mds_adapter.get_diagnosis_and_gps_lists()

Created test case for the get_diagnosis_and_gps_lists() function.
Created a test case data to go with it.