os.path.exists should be mocked in test case

This commit mocks os.path.exists in the test case
test_start_iscsi_target_fail_wait_daemon in
extensions.iscsi.TestISCSIExtension.  If this isn't
mocked, the file can coincidentally exist on the
environment and can cause failure.

Change-Id: Ibaa8fcae51faaaefc2764411d02621f347d99c03

ironic_python_agent/tests/extensions/iscsi.py

@@ -16,6 +16,7 @@
 #    under the License.
 
 import mock
+import os
 import time
 
 from oslo_concurrency import processutils
@@ -64,6 +65,7 @@ class TestISCSIExtension(test_base.BaseTestCase):
         self.assertEqual({'iscsi_target_iqn': self.fake_iqn},
                           result.command_result)
 
+    @mock.patch.object(os.path, 'exists', lambda x: False)
     def test_start_iscsi_target_fail_wait_daemon(self, mock_execute,
                                                  mock_dispatch):
         mock_dispatch.return_value = self.fake_dev