Py3: Replace six.moves imports

Replace six.moves and six.StringIO/BytesIO imports with cannonical
Python 3 packages.

Note: six.moves.input behaves differently than builtin input function.
Therefore I left six.moves.input for now.

See: https://pagure.io/freeipa/issue/7715
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>

ipaserver/plugins/otptoken.py

@@ -30,11 +30,11 @@ from ipalib.request import context
 from ipapython.dn import DN
 
 import base64
+import urllib
 import uuid
 import os
 
 import six
-from six.moves import urllib
 
 if six.PY3:
     unicode = str