Replace mock by unittest.mock in 2 forgotten cases

We replaced usage of third party mock by the standard library in:
https://review.opendev.org/#/c/721021/
There are 2 forgotten occurrences where we still use the third
party mock, the patch fixes that.

Change-Id: I7d00be25bb0b70ce55e27790df33d9134c2a52ae

tempest/tests/cmd/test_workspace.py

@@ -16,12 +16,12 @@ import os
 import shutil
 import subprocess
 import tempfile
-
-from mock import patch
+from unittest.mock import patch
 try:
     from StringIO import StringIO
 except ImportError:
     from io import StringIO
+
 from tempest.cmd import workspace
 from tempest.lib.common.utils import data_utils
 from tempest.tests import base

tempest/tests/lib/cmd/test_check_uuid.py

@@ -10,10 +10,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import tempfile
-
 import importlib
-import mock
+import tempfile
+from unittest import mock
 
 from tempest.lib.cmd import check_uuid
 from tempest.tests import base