Remove invalid test case of mistralclient

Delete 'test_ex_invalid_status_changing' negative test case, the reason of
its working before is because there is a bug[1], which was fixed[2]
several days ago.

[1]: https://bugs.launchpad.net/mistral/+bug/1491541
[2]: https://review.openstack.org/219870

Change-Id: Ic50a8cce0a94da83a138bd5968fe55060e7065c0
Closes-Bug: #1493183

mistralclient/tests/functional/cli/v2/cli_tests_v2.py

@@ -928,15 +928,6 @@ class NegativeCLITests(base_v2.MistralClientTestBase):
                           'execution-create empty',
                           params=wf[1]['Name'])
 
-    def test_ex_invalid_status_changing(self):
-        wf = self.workflow_create(self.wf_def)
-        execution = self.execution_create(params=wf[0]['Name'])
-        exec_id = self.get_value_of_field(execution, 'ID')
-        self.assertRaises(exceptions.CommandFailed,
-                          self.mistral_admin,
-                          'execution-update',
-                          params='%s -s ERROR' % exec_id)
-
     def test_ex_update_both_state_and_description(self):
         wf = self.workflow_create(self.wf_def)
         execution = self.execution_create(params=wf[0]['Name'])