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/rpcserver.py

@@ -29,6 +29,9 @@ import logging
 from xml.sax.saxutils import escape
 import os
 import traceback
+from io import BytesIO
+from urllib.parse import parse_qs
+from xmlrpc.client import Fault
 
 import gssapi
 import requests
@@ -37,11 +40,6 @@ import ldap.controls
 from pyasn1.type import univ, namedtype
 from pyasn1.codec.ber import encoder
 import six
-# pylint: disable=import-error
-from six.moves.urllib.parse import parse_qs
-from six.moves.xmlrpc_client import Fault
-# pylint: enable=import-error
-from six import BytesIO
 
 from ipalib import plugable, errors
 from ipalib.capabilities import VERSION_WITHOUT_CAPABILITIES