Port EMC scaleio to Python 3

Port EMC scaleio to Python 3

* Import urllib modules using six.moves.urllib
* MockHTTPSResponse: encode HTTP body to UTF-8 if it's Unicode,
  replace six.string_types with (bytes, six.text_type).
* _id_to_base64(): catch also binascii.Error when calling
  b16decode(); encode name to UTF-8 before calling b64encode();
  decode b64encode() from ASCII on Python 3 to get Unicode.
* tox.ini: add cinder.tests.unit.volume.drivers.emc.scaleio
  to Python 3.4

Partial-Implements: blueprint cinder-python3
Change-Id: I93353d48f80971528f47c9291cd04e198632dd0b