Fix Python 3 issues in utils

Fix Python 3 issues in utils

* Replace string.split(key_file, ',') with key_file.split(','):
  the string.split() function was removed in Python 3, use the
  str.split() method instead
* Fix conf_fixture: import backup_enable_progress_timer and
  backup_swift_enable_progress_timer options. This change is required
  to run tests using testtools (it's now possible yet to run tests on
  Python 3 using testr).
* hash_file(): use b'' (bytes) for the sentinel, not '' (unicode), when
  reading the input binary file
* test_hash_file() requires a binary file (bytes), not a text file
  (unicode)
* Get the builtin open() function from six.moves.builtins instead of
  getting it from __builtin__ to mock the open() function. The
  __builtin__ module was renamed to builtins in Python 3.
* sanitize_hostname(): on Python 3, decode back the hostname from Latin1
  to work on a native string (Unicode)
* replace reduce() with six.moves.reduce(): the Python 2 builtin
  reduce() function was moved to the functools module in Python 3
* convert_version_to_str(): fix integer division, use a//b, not a/b
* convert_version_to_str(): replace reduce() with ''.join() with map(str)

Blueprint cinder-python3
Change-Id: If7b8f50c6a8b0a5044c2c7108b2b0293dddafff3