Port drbdmanagedrv driver to Python 3

Port drbdmanagedrv driver to Python 3

* Replace map() with a list-comprehension where a list is expected
* Replace apply(fn, args) with fn(*args)
* Use str.replace() to remove "{" and "}" characters in _clean_uuid(),
  instead of using str.translate()
* Use literal syntax to create a new dictionary instead of using
  dict() + dict.items()
* tox.ini: add cinder.tests.unit.test_drbdmanagedrv to Python 3.4

Blueprint cinder-python3
Change-Id: I4cb3ae422381442b778de024882e75f31eded5eb