Use unittest.mock instead of mock

The mock third party library was needed for mock support in py2
runtimes. Since we now only support py36 and later, we can use the
standard lib unittest.mock module instead

Change-Id: I8ea9821fbf7a63b819f7042a2c9729ce38742f22

tripleo_ansible/tests/modules/test_metalsmith_instances.py

@@ -13,8 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
-
+from unittest import mock
 from tripleo_ansible.ansible_plugins.modules import metalsmith_instances as mi
 from tripleo_ansible.tests import base as tests_base
 

tripleo_ansible/tests/modules/test_tripleo_deploy_artifacts.py

@@ -16,7 +16,7 @@
 from tripleo_ansible.ansible_plugins.modules import tripleo_deploy_artifacts
 from tripleo_ansible.tests import base as tests_base
 
-import mock
+from unittest import mock
 
 
 class TestTripleoDeployArtifacts(tests_base.TestCase):

tripleo_ansible/tests/modules/test_tripleo_diff_exec.py

@@ -15,8 +15,7 @@
 
 from tripleo_ansible.ansible_plugins.modules import tripleo_diff_exec
 from tripleo_ansible.tests import base as tests_base
-
-import mock
+from unittest import mock
 
 
 class TestTripleoDiffExec(tests_base.TestCase):

tripleo_ansible/tests/modules/test_tripleo_list_overclouds.py

@@ -13,7 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
+from unittest import mock
 
 from heatclient import exc as heat_exc
 

tripleo_ansible/tests/modules/test_tripleo_os_net_config_mappings.py

@@ -16,8 +16,7 @@
 from tripleo_ansible.ansible_plugins.modules import (
     tripleo_os_net_config_mappings)
 from tripleo_ansible.tests import base as tests_base
-
-import mock
+from unittest import mock
 
 
 @mock.patch('tripleo_ansible.ansible_plugins.modules.'

tripleo_ansible/tests/plugins/module_utils/test_baremetal_deploy.py

@@ -14,7 +14,7 @@
 #    under the License.
 
 import metalsmith
-import mock
+from unittest import mock
 from openstack import exceptions as sdk_exc
 
 from tripleo_ansible.tests import base