Use unittest.mock instead of third party mock

Now that we no longer support py27, we can use the standard library
unittest.mock module instead of the third party mock lib.

Change-Id: I7a7b0090139a72a06ec98d22e27e015307c3aec3
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

translator/hot/tosca/tests/test_tosca_compute.py

@@ -10,7 +10,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
+from unittest import mock
 
 from toscaparser.nodetemplate import NodeTemplate
 from toscaparser.tests.base import TestCase

translator/osc/v1/tests/fakes.py

@@ -11,8 +11,7 @@
 #   under the License.
 
 import sys
-
-import mock
+from unittest import mock
 
 
 class FakeApp(object):

translator/osc/v1/tests/test_translate.py

@@ -10,8 +10,8 @@
 #   License for the specific language governing permissions and limitations
 #   under the License.
 
-import mock
 import testtools
+from unittest import mock
 
 try:
     from StringIO import StringIO

translator/tests/test_conf.py

@@ -10,8 +10,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
 import os
+from unittest import mock
 
 from translator.conf.config import ConfigProvider as translatorConfig
 from translator.tests.base import TestCase

translator/tests/test_shell.py

@@ -12,10 +12,10 @@
 
 
 import json
-import mock
 import os
 import shutil
 import tempfile
+from unittest import mock
 
 from toscaparser.common import exception
 from toscaparser.utils.gettextutils import _