Fails test under python 3.6

[Thomas Goirand]

Under Python 3.6, there's the below issue with unit tests when building the Debian package. Note that for me, it worked in Python 2.7 and 3.5.

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FAIL: proliantutils.tests.ilo.test_firmware_controller.FirmwareImageExtractorTestCase.test_successive_calls_to_extract_method
proliantutils.tests.ilo.test_firmware_controller.FirmwareImageExtractorTestCase.test_successive_calls_to_extract_method
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_StringException: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
  File "/home/zigo/sources/openstack/pike/python-proliantutils/build-area/python-proliantutils-2.4.1/proliantutils/tests/ilo/test_firmware_controller.py", line 473, in test_successive_calls_to_extract_method
    raw_fw_file, is_extracted = fw_img_extractor.extract()
  File "/home/zigo/sources/openstack/pike/python-proliantutils/build-area/python-proliantutils-2.4.1/proliantutils/ilo/firmware_controller.py", line 273, in extract
    extract_path = os.path.join(temp_dir, self.fw_filename)
  File "/usr/lib/python3.6/posixpath.py", line 78, in join
    a = os.fspath(a)
TypeError: expected str, bytes or os.PathLike object, not MagicMock