Don't use deprecated configparser.readfp

Running verify_tempest_config, it complains with:
  /opt/stack/tempest/tempest/cmd/verify_tempest_config.py:444:
  DeprecationWarning: This method will be removed in future versions.
  Use 'parser.read_file()' instead.

Use read_file.

Also, remove one extra use of six in this file.

Change-Id: Ia32df8e2be29bb0951efd08db9eed9e67d749e1f

tempest/cmd/verify_tempest_config.py

@@ -60,16 +60,16 @@ name (tempest.conf) is overridden.
 """
 
 import argparse
+import configparser
 import os
 import re
 import sys
 import traceback
+from urllib import parse as urlparse
 
 from cliff import command
 from oslo_log import log as logging
 from oslo_serialization import jsonutils as json
-from six import moves
-from six.moves.urllib import parse as urlparse
 
 from tempest import clients
 from tempest.common import credentials_factory as credentials
@@ -439,9 +439,9 @@ def main(opts=None):
 
     if update:
         conf_file = _get_config_file()
-        CONF_PARSER = moves.configparser.ConfigParser()
+        CONF_PARSER = configparser.ConfigParser()
         CONF_PARSER.optionxform = str
-        CONF_PARSER.readfp(conf_file)
+        CONF_PARSER.read_file(conf_file)
 
     # Indicate not to create network resources as part of getting credentials
     net_resources = {