used unittest.mock instead of mock

Author: harshitasao

kubernetes/base/config/exec_provider_test.py

@@ -15,7 +15,7 @@
 import os
 import unittest
 
-import mock
+from unittest import mock
 
 from .config_exception import ConfigException
 from .exec_provider import ExecProvider

kubernetes/base/config/kube_config_test.py

@@ -22,7 +22,7 @@
 import unittest
 from collections import namedtuple
 
-import mock
+from unittest import mock
 import yaml
 from six import PY3, next
 

kubernetes/base/watch/watch_test.py

@@ -14,7 +14,7 @@
 
 import unittest
 
-from mock import Mock, call
+from unittest.mock import Mock, call
 
 from kubernetes import client