Fix Python 3 issues in Windows tests

Fix Python 3 issues in Windows tests

* Replace __builtin__ with six.moves.builtins
* tox.ini: add the following tests to Python 3.4

  - cinder.tests.unit.windows.test_smbfs
  - cinder.tests.unit.windows.test_vhdutils
  - cinder.tests.unit.windows.test_windows
  - cinder.tests.unit.windows.test_windows_remotefs
  - cinder.tests.unit.windows.test_windows_utils

This change requires the Python 3 fixes in os-brick.

Blueprint cinder-python3
Change-Id: I1ffa65745923459e993e81d8a95a39e19c1bd1e4