TST: use ensure_clean rather than explicit os.remove

[jreback]

~/pandas-dev$ grep -r os.remove pandas/tests/
pandas/tests/io/excel/test_openpyxl.py:    os.remove(filename)
pandas/tests/io/excel/test_writers.py:    #     os.remove(filename)
pandas/tests/io/excel/test_writers.py:    #     os.remove(filename)
pandas/tests/io/pytables/common.py:            os.remove(path)

we should also create a rule in code_checks.sh to avoid doing this in the future

[jnecus]

take

[phs-sakshi]

Can I take up this issue?